feat: add security response headers middleware (closes #98 )

Add SecurityHeaders() to internal/middleware and register it in the global middleware stack so every response - dashboard, embedded static assets, healthchecks, JSON API, and metrics - carries the six response headers required by REPO_POLICIES.md before tagging 1.0: Strict-Transport-Security: max-age=31536000; includeSubDomains Content-Security-Policy: default-src 'self'; script-src 'none'; style-src 'self'; img-src 'self'; font-src 'none'; connect-src 'none'; object-src 'none'; base-uri 'none'; form-action 'none'; frame-ancestors 'none' X-Frame-Options: DENY X-Content-Type-Options: nosniff Referrer-Policy: no-referrer Permissions-Policy: unused browser features denied The dashboard template ships no JavaScript, no inline styles, no inline event handlers and no images, and its only subresource is the embedded stylesheet at /s/css/tailwind.min.css, so the policy needs neither unsafe-inline nor unsafe-eval. frame-ancestors 'none' is the primary anti-framing control with X-Frame-Options as the legacy fallback. HSTS is emitted unconditionally rather than gated on r.TLS, because the service runs behind a TLS-terminating proxy and the browser must still enforce HTTPS end to end. The headers are set before the request reaches the next handler, so they are present on error responses too, including recovered panics and request timeouts. Tests cover each header's exact value, the CSP's required and forbidden directives, presence on a 500 response, and a render of the real dashboard through the middleware confirming the page still references its stylesheet.
2026-09-21 07:59:18 +00:00
28 changed files with 1126 additions and 1616 deletions
@@ -10,20 +10,14 @@ run:
 linters:
  default: all
  enable:
    # Successor to the deprecated gomodguard. Named explicitly, rather than
    # left to `default: all`, because it carries the module policy below.
    - gomodguard_v2
  disable:
    # Genuinely incompatible with project patterns
    - exhaustruct      # Requires all struct fields
    - depguard         # Dependency allow/block lists
    - godot            # Requires comments to end with periods
    - wsl              # Deprecated, replaced by wsl_v5
    - wrapcheck        # Too verbose for internal packages
    - varnamelen       # Short names like db, id are idiomatic Go
    # Deprecated: the warning is attached to the old name, so it is
    # silenced by disabling that name, not by enabling the successor.
    - wsl              # Deprecated, replaced by wsl_v5
    - gomodguard       # Deprecated, replaced by gomodguard_v2
  settings:
    lll:
      line-length: 88
@@ -34,68 +28,6 @@ linters:
      max-complexity: 15
    dupl:
      threshold: 100
    depguard:
      # Test-support code must not be compiled into the shipped binary. A
      # test-support package exists to hand a test privileges the program
      # itself must never have, so a file that is not a test must not import
      # one. Test files, and the files inside a package whose directory name
      # ends in `test`, are where that code belongs, and are exempt.
      #
      # The deny list below is the one part of this file a repository is
      # expected to extend, and the only part it may. depguard matches an
      # import path against a list of prefixes, so it cannot be told "any path
      # whose last segment ends in test"; a repository's own test-support
      # packages have to be named here one at a time, by full import path,
      # under a module path that differs from repository to repository. Add
      # them; change nothing else.
      rules:
        test-support:
          list-mode: lax
          files:
            - "$all"
            - "!$test"
            - "!**/*test/**"
          deny:
            - pkg: net/http/httptest
              desc: >-
                Test-support code belongs in test files and in packages whose
                directory name ends in test, not in the shipped binary.
            - pkg: sneak.berlin/go/dnswatcher/internal/livednstest
              desc: >-
                Live-DNS test support belongs in test files and in packages
                whose directory name ends in test, not in the shipped binary.
    # Only decisions already recorded in the Go package defaults are
    # listed here. Every entry matches the module path exactly.
    gomodguard_v2:
      blocked:
        - module: github.com/rs/zerolog
          recommendations:
            - log/slog
          reason: "Structured logging is stdlib log/slog."
        # One entry per pre-fork module path, because the later releases
        # are separate paths. A prefix match would be shorter but would
        # also reach github.com/go-redis/redismock, the test double for
        # the successor these entries recommend.
        - module: github.com/go-redis/redis
          recommendations:
            - github.com/redis/go-redis/v9
          reason: "Pre-fork module; use the maintained go-redis v9."
        - module: github.com/go-redis/redis/v7
          recommendations:
            - github.com/redis/go-redis/v9
          reason: "Pre-fork module; use the maintained go-redis v9."
        - module: github.com/go-redis/redis/v8
          recommendations:
            - github.com/redis/go-redis/v9
          reason: "Pre-fork module; use the maintained go-redis v9."
        - module: github.com/sergi/go-diff
          recommendations:
            - github.com/aymanbagabas/go-udiff
          reason: "No unified diff output; use go-udiff."
        - module: github.com/hexops/gotextdiff
          recommendations:
            - github.com/aymanbagabas/go-udiff
          reason: "Unmaintained fork; use go-udiff."
 issues:
  max-issues-per-linter: 0
@@ -2,7 +2,6 @@
 # The linter is invoked directly rather than through `make lint`: that
 # target shells out to `docker build -f Dockerfile.lint`, and there is
 # no docker daemon inside a docker build.
 # script/cibuild and script/docker name this stage in --no-cache-filter.
 # golangci/golangci-lint:v2.12.2 (Debian-based), 2026-08-10
 FROM golangci/golangci-lint:v2.12.2@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240 AS lint
@@ -16,7 +15,6 @@ RUN make fmt-check
 RUN golangci-lint run --config .golangci.yml ./...
 # Build stage
 # script/cibuild and script/docker name this stage in --no-cache-filter.
 # golang 1.25-alpine, 2026-02-28
 FROM golang@sha256:f6751d823c26342f9506c03797d2527668d095b0a15f1862cddb4d927a7a4ced AS builder
@@ -43,33 +41,15 @@ FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4
 RUN apk add --no-cache ca-certificates tzdata
-COPY --from=builder /src/bin/dnswatcher /usr/local/bin/dnswatcher
+WORKDIR /app
-# Run as an unprivileged user that owns the data directory. A fresh named
+COPY --from=builder /src/bin/dnswatcher /app/dnswatcher
-# volume inherits this ownership; a bind-mounted host directory must be
+
-# owned by uid 10001 (see "Running under upaas" in README.md), or startup
+# Create data directory
-# fails.
+RUN mkdir -p /var/lib/dnswatcher
 RUN addgroup -S -g 10001 dnswatcher \
    && adduser -S -G dnswatcher -u 10001 dnswatcher \
    && mkdir -p /var/lib/dnswatcher \
    && chown dnswatcher:dnswatcher /var/lib/dnswatcher
 ENV DNSWATCHER_DATA_DIR=/var/lib/dnswatcher
 # Config loading also reads a `.env` file and a file named `dnswatcher`
 # (any config extension, or none) from the working directory. `/` holds
 # neither, so every setting comes from the environment. Do not make the
 # data directory, or the binary's directory, the working directory.
 WORKDIR /
 USER dnswatcher
 EXPOSE 8080
-# busybox wget (already in alpine) probes the health endpoint every 10
+ENTRYPOINT ["/app/dnswatcher"]
 # seconds, so the container is healthy well before upaas reads its health
 # 60 seconds after a deploy and fails the deploy unless it is healthy.
 HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=3 \
    CMD wget -q -O /dev/null "http://127.0.0.1:${PORT:-8080}/.well-known/healthcheck" || exit 1
 ENTRYPOINT ["/usr/local/bin/dnswatcher"]
@@ -61,10 +61,6 @@ rejected.
  record types: A, AAAA, CNAME, MX, TXT, SRV, CAA, NS.
 - Stores results **per nameserver**. The state for a hostname is not a
  merged view — it is a map from nameserver to record set.
 - DNS names inside record values (CNAME, MX, SRV and NS targets) are
  stored in lower case, because names are case-insensitive and
  nameservers may answer in any letter case. TXT and CAA values keep
  their letter case; they are not lower-cased.
 - Any observable change in any nameserver's response triggers a
  notification. This includes:
  - **Record change**: A nameserver returns different records than it
@@ -74,15 +70,8 @@ rejected.
    This is distinct from "responded with no records."
  - **NS recovery**: A previously-unreachable nameserver starts
    responding again.
-  - **Inconsistency detected**: Two nameservers return different record
+  - **Inconsistency detected**: Two nameservers that previously agreed
-    sets for the same hostname and did not already differ on the previous
+    now return different record sets for the same hostname.
    check. Every pair of nameservers is compared. The alert is sent once
    for each such pair, on the check where they start to disagree, and not
    again while they keep disagreeing, including after a restart. A
    nameserver that was not in the previous check (newly added, or back
    after dropping out) and answers differently is reported on the check
    where it appears. If a pair agrees again and later disagrees, the
    alert is sent again.
 ### TCP Port Monitoring
@@ -278,8 +267,6 @@ internal/
  tlscheck/tlscheck.go        TLS certificate inspector
  notify/notify.go             Notification service (Slack, Mattermost, ntfy)
  watcher/watcher.go           Main monitoring orchestrator and scheduler
  livednstest/livednstest.go   Retry and concurrency limit for tests
                               against live DNS (imported only by tests)
 ```
 ### Design Principles
@@ -478,13 +465,9 @@ them. We provide:
 - `script/fmt` — format all code (gofmt -s, goimports)
 - `script/fmt-check` — check formatting (read-only)
 - `script/check` — run test, lint, and fmt-check
- `script/docker` — build the Docker image tagged via `script/projectname`, with
+- `script/docker` — build the Docker image tagged via
-  `--no-cache-filter=lint,builder` so the lint stage and the builder stage,
+  `script/projectname`
-  which runs the tests, run on every invocation
+- `script/cibuild` — CI entrypoint: plain `docker build .`
 - `script/cibuild` — CI entrypoint: `docker build` with
  `--no-cache-filter=lint,builder`, so the lint stage and the builder stage,
  which runs the tests, run on every invocation, because a cached build lints
  nothing and queries no DNS
 - `script/precommit` — run by the git pre-commit hook; `go mod tidy`
  guard, then `script/check`
 - `script/install-precommit` — install the git pre-commit hook
@@ -525,57 +508,11 @@ docker run -d \
 ---
 ## Running under upaas
 [upaas](https://git.eeqj.de/sneak/upaas) builds the image from this
 repository's `Dockerfile` and runs it. The app needs:
 - **Branch:** `prod`. `prod` is cut from `main`, and merging a `main` to
  `prod` pull request is a deploy.
 - **Volume:** one host directory mounted at `/var/lib/dnswatcher`, where
  the state file lives. upaas bind-mounts the host path it is given and
  does not create it. The container runs as uid 10001 and does not start
  unless it can write there. Create the directory before the first
  deploy:
  ```sh
  mkdir -p /path/to/data
  chown 10001:10001 /path/to/data
  chmod 700 /path/to/data
  ```
 - **Network and port:** the dashboard is unauthenticated and shows every
  watched name and recent alert, and upaas publishes every mapped port on
  all interfaces of the host
  ([upaas issue 113](https://git.eeqj.de/sneak/upaas/issues/113)). Add a
  port mapping to container port `8080` only if the dashboard should be
  public. Otherwise add none: set the app's Docker network in upaas to
  your reverse proxy's Docker network, and the proxy reaches the app at
  `upaas-` followed by the app name, port `8080`.
 - **Required environment:** `DNSWATCHER_TARGETS`, a comma-separated list
  of the domains and hostnames to watch. dnswatcher refuses to start
  without it.
 - **Recommended environment:** at least one notification endpoint
  (`DNSWATCHER_SLACK_WEBHOOK`, `DNSWATCHER_MATTERMOST_WEBHOOK`,
  `DNSWATCHER_NTFY_TOPIC`); without one, changes show only on the
  dashboard. `DNSWATCHER_METRICS_USERNAME` and
  `DNSWATCHER_METRICS_PASSWORD` serve `/metrics` behind basic auth.
 - **Leave unset:** `DNSWATCHER_DATA_DIR`, which the image sets to
  `/var/lib/dnswatcher`, and `PORT`, which defaults to `8080`. Every
  setting comes from the environment; the image holds no config file.
 - **Health check:** the image's own, which requests
  `/.well-known/healthcheck` every 10 seconds. upaas reads the
  container's health 60 seconds after a deploy and marks the deploy
  failed unless it is `healthy`.
 ---
 ## Monitoring Lifecycle
-1. **Startup**: Check that the data directory can be written, and exit
+1. **Startup**: Load state from disk. If no state file exists, start
-   with an error naming it if not. Load state from disk. If no state
+   with empty state (first check will establish baseline without
-   file exists, start with empty state (first check will establish
+   triggering change notifications).
   baseline without triggering change notifications).
 2. **Initial check**: Immediately perform all DNS, port, and TLS checks
   on startup.
 3. **Periodic checks** (DNS always runs first):
@@ -2,12 +2,8 @@
 ## DNS Resolution Tests
-DNS is never mocked in this project, not in tests and not anywhere
+All resolver tests **MUST** use live queries against real DNS servers.
-else; see the README section "No DNS mocking. Ever." Every test that
+No mocking of the DNS client layer is permitted.
 looks something up in DNS **MUST** query live DNS servers, never a
 stand-in. Logic that works on record data, such as comparing or
 formatting records, may be tested on that data directly with no
 lookup.
 ### Rationale
@@ -25,18 +21,14 @@ real servers ensures the resolver works correctly in production.
 - Query timeout is calibrated to 3× maximum antipodal RTT (~300ms)
  plus processing margin
 - Root server fan-out is limited to reduce parallel query load
 - Live lookups that expect an answer go through `internal/livednstest`,
  which limits how many run at once in a test binary and retries a
  lookup that got none
 - Flaky failures from transient network issues are acceptable and
  should be investigated as potential resolver bugs, not papered over
  with mocks or skip flags
 ### What NOT to do
- **Do not mock, fake or stub DNS** anywhere: no stand-in `DNSClient`,
+- **Do not mock `DNSClient`** for resolver tests (the mock constructor
-  no stand-in for the watcher's `DNSResolver`, no fake DNS server, no
+  exists for unit-testing other packages that consume the resolver)
  canned responses
 - **Do not add `-short` flags** to skip slow tests
 - **Do not increase `-timeout`** to hide hanging queries
 - **Do not remove `-count=1` from `script/test`** — Go's test cache
@@ -1,100 +1,247 @@
 # Workflow
-* branch (from `next`)
+* branch (from `main`)
 * do the work in Next Step
 * move Next Step to the top of Completed Steps
 * move the top item of Future Steps into Next Step
 * commit (`TODO.md` changes in the same commit as the work)
 * merge to `main` if the branch is not protected, otherwise open a PR
 * push
 * open a PR against `next`
 # Status
-pre-1.0. No git tags. Work lands on `next` by PR. Open work for 1.0 is tracked
+pre-1.0. No git tags. Core resolver work in flight on feature/resolver
-on the 1.0 milestone: https://git.eeqj.de/sneak/dnswatcher/milestone/7
+(dirty: internal/resolver/resolver_test.go). Local checkout has diverged
 from origin: origin/main is 8 commits ahead (watcher orchestrator,
 unified TARGETS) and origin/feature/resolver already contains the full
 iterative resolver implementation with hermetic mocked tests.
 # Next Step
-NS failure and NS recovery notifications:
+Add the README sections required by policy (Description, Getting Started,
-https://git.eeqj.de/sneak/dnswatcher/issues/104
+Rationale, Design, TODO, License, Author) if any are still missing.
 # Completed Steps
 - 2026-10-01: `TODO.md` brought up to date: open issues listed by URL, every
  Completed Steps entry cut to at most two lines (closes #146).
 - 2026-09-29: the live-DNS test package is renamed `internal/livednstest`;
  `make lint` fails when program code imports it (closes #164).
 - 2026-09-29: `.golangci.yml` re-fetched from `sneak/prompts`, with
  `gomodguard_v2` and the org `depguard` `test-support` rule (closes #123).
 - 2026-09-29: watcher and resolver tests that look something up in DNS use the
  real resolver against live DNS servers (closes #159).
 - 2026-09-28: the inconsistency alert is sent once, when two nameservers start
  to disagree; every pair of nameservers is compared (closes #158).
 - 2026-09-28: DNS names in record values (CNAME, MX, SRV and NS targets) are
  lower-cased, so letter case alone is not a change (closes #157).
 - 2026-09-28: lint and tests run on every build: `script/cibuild` and
  `script/docker` pass `--no-cache-filter=lint,builder` (closes #115).
 - 2026-09-28: the server timeout test drives `Run` and checks the timeouts on
  the `http.Server` it serves (closes #120).
 - 2026-09-28: upaas deploy readiness: the image runs as user `dnswatcher` with a
  `HEALTHCHECK`; README "Running under upaas" (closes #147).
 - 2026-09-21: added behavioural tests for `internal/globals`,
  `internal/healthcheck`, and `internal/logger` (closes #110).
 - 2026-09-21: `go mod tidy` dropped the redundant `golang.org/x/sync`
  `// indirect` line so `script/bootstrap` leaves a clean tree (#132)
- 2026-08-10: comment-only corrections to `script/bootstrap`, `script/cibuild`
+- 2026-08-10: comment-only corrections to `script/bootstrap`,
-  and `Dockerfile.lint`; no behaviour changed.
+  `script/cibuild`, and `Dockerfile.lint`. The `goimports` pin in
- 2026-08-10: MIT `LICENSE` added at the repository root; the README's first
+  `script/bootstrap` was justified by a claim that `script/fmt-check`
-  line and License section name the licence.
+  runs it on the host; it does not (it runs `gofmt -l .` only), so the
- 2026-08-10: policy scaffold present: `REPO_POLICIES.md`, `.editorconfig`,
+  header now credits `script/fmt` alone. `script/cibuild` still claimed
-  `.dockerignore`, CI workflow, `make fmt-check`, `make docker`, `make hooks`.
+  the `Dockerfile` runs `make check`, which stopped being true when
- 2026-08-10: Go's test cache disabled in `script/test` (`-count=1`), so every
+  linting moved to its own stage; it now describes the lint stage
-  run queries live DNS; a failed run is rerun with `-v`.
+  (`make fmt-check` plus `golangci-lint`) and the builder stage
- 2026-08-10: live-DNS tests made robust rather than gated (#93): a limit on
+  (`make test`, `make build`). The `docker`-missing warning in
-  concurrent lookups, retries, and a quorum across nameservers.
+  `script/bootstrap` reads as one sentence instead of three fragments
- 2026-08-10: all linting moved into Docker: `script/lint` builds
+  each re-prefixed with `bootstrap:`. `Dockerfile.lint` now records the
-  `Dockerfile.lint`, and the root `Dockerfile` has its own lint stage.
+  residual risk of omitting `golangci-lint config verify`: unknown
- 2026-08-09: in-flight notification deliveries are drained at shutdown, bounded
+  top-level keys in `.golangci.yml` are silently ignored, so a mistyped
-  by the shutdown deadline (#106).
+  key lints clean while applying nothing. No behaviour changed
- 2026-08-09: `http.Server` sets all four socket timeouts; `WriteTimeout` stays
+- 2026-08-10: MIT `LICENSE` added at the repository root, closing the
-  above the 60s handler timeout (#99).
+  last gap in `REPO_POLICIES.md`'s required-minimum file list and
- 2026-08-09: `SecurityHeaders()` middleware sets HSTS, CSP and the other
+  removing the all-rights-reserved default that would otherwise have
-  security headers `REPO_POLICIES.md` requires on every response.
+  shipped with a 1.0 tag. The licence choice is the standing org policy
- 2026-08-07: golangci-lint bumped to v2.12.2 and `.golangci.yml` set to the org
+  (any public repo lacking a licence gets MIT; a private repo with no
-  config; fixed the resulting `goconst`, `dupl` and `lll` findings.
+  licence is already all-rights-reserved), and this repo is public. The
- 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints, Makefile
+  file holds the canonical MIT text byte-for-byte with only the
-  shims, README Entrypoints section
+  copyright line filled in (`Copyright (c) 2026 sneak`); no clauses were
- 2026-02-20: iterative DNS resolver implemented
+  added, removed, or reflowed. `README.md`'s first line now names the
- 2026-02-20: CI actions and go install refs pinned to commit SHAs; Gitea
+  licence, as the Description requirement demands, and the License
-  Actions workflow added
+  section states MIT and points at the file instead of saying the choice
  is pending. `make fmt` covers only Go sources (`gofmt -s`,
  `goimports`), so it cannot reflow `LICENSE`
 - 2026-08-10: the policy scaffold (`REPO_POLICIES.md`, `.editorconfig`,
  `.dockerignore`, `.gitea/workflows/check.yml`, and the `fmt-check`,
  `docker`, and hooks Makefile targets) is present; it landed piecemeal
  across the scripts-to-rule-them-all and policy commits rather than as
  the single commit this file once planned
 - 2026-08-10: Go's test cache disabled for `script/test` via `-count=1`,
  so every invocation actually executes. A cached pass replays an
  earlier run's output without querying DNS at all, which in this repo
  means the suite's entire premise goes unexercised while the run
  reports green in under a second. The conditional verbose rerun that
  `REPO_POLICIES.md` mandates was added at the same time (the primary
  run had been unconditionally `-v`): quiet first, `-v` only on
  failure, `-count=1` on both, and exit 1 forced regardless of the
  rerun's result so a flake passing the second time cannot turn the
  build green. `-timeout 90s` left alone as the deliberate backstop
  above the 60s hard cap. Uncached suite runs ~4s, well inside the 20s
  target
 - 2026-08-10: live-DNS test flakiness addressed by robustness rather
  than gating, per the owner's ruling on #93: new
  `internal/resolver/livedns_test.go` adds a package-wide concurrency
  gate (so parallel tests stop bursting at the first root server),
  retry with exponential backoff on transport failures only, and
  quorum instead of unanimity for multi-nameserver assertions. Quorum
  tolerates silence only: every per-nameserver status must be in a
  closed allowlist (`ok`/`timeout`/`error`, or
  `nxdomain`/`timeout`/`error`), so a wrong answer from a minority —
  `nodata` today, any status added later — fails the test instead of
  sliding through under the majority. The
  `make test` cap moved to the new org-wide 60s hard cap / 20s target
  with a 90s `-timeout` backstop; `REPO_POLICIES.md` re-vendored
  byte-identical from `sneak/prompts`. No mocks, no `-short`, no build
  tags, no skips, and no change to production resolver behaviour
 - 2026-08-10: all linting moved into Docker: new root `Dockerfile.lint`
  on the digest-pinned `golangci/golangci-lint:v2.12.2` image,
  `script/lint` reduced to a thin wrapper that builds it with
  `--no-cache-filter=lint` so the linter actually executes every run,
  golangci-lint install dropped from `script/bootstrap` (goimports
  stays, `script/fmt` needs it on the host), and the root `Dockerfile`
  given its own lint stage so its build no longer recurses through
  `make check` into `script/lint`. `golangci-lint config verify` is
  deliberately omitted: it fetches its schema over an unpinned live
  HTTPS call
 - 2026-08-09: in-flight notification deliveries are now drained at
  shutdown (#106): `notify.New` registers an fx `OnStop` hook that waits
  on a `sync.WaitGroup` of tracked delivery goroutines, bounded by the
  `OnStop` context; on expiry the outstanding count is logged at warn
  level and parked retry backoffs are released instead of being dropped
  silently, and deliveries submitted after the drain begins are refused
  so shutdown cannot be extended indefinitely; an `OnStop` context that
  is already expired on entry with nothing outstanding drains quietly
  rather than warning about deliveries that were never abandoned
 - 2026-08-09: `http.Server` now sets all four socket-level timeouts
  (`ReadTimeout` 15s, `ReadHeaderTimeout` 10s, `WriteTimeout` 75s,
  `IdleTimeout` 120s) as named constants in `internal/server/server.go`,
  closing the slowloris / unreaped-keep-alive exposure required by
  `REPO_POLICIES.md` before 1.0; `WriteTimeout` is deliberately greater
  than the 60s `chimw.Timeout` handler budget so that budget stays
  reachable, and tests in `internal/server` pin both the non-zero
  values and that relationship (#99)
 - 2026-08-09: security response headers middleware
  (`SecurityHeaders()` in `internal/middleware/middleware.go`)
  registered globally in `internal/server/routes.go`, so HSTS, CSP,
  `X-Frame-Options`, `X-Content-Type-Options`, `Referrer-Policy`, and
  `Permissions-Policy` are set on every response including `/s/...` and
  `/metrics`; the CSP needs no `unsafe-inline`/`unsafe-eval` because the
  dashboard ships no JavaScript and no inline styles; HSTS is emitted
  unconditionally per policy (TLS-terminating proxy in front). Remaining
  1.0 hardening items — `http.Server` timeouts, request body limits,
  rate limiting, CORS scoping — are tracked separately
 - 2026-08-07: golangci-lint bumped to v2.12.2 (commit-pinned installs
  in `Dockerfile` and `script/bootstrap`); `.golangci.yml` set to the
  org-standard v2-schema config used across the org's repos
  (owner-authorized; same file is being landed as canonical via prompts
  PR #24), with settings under `linters.settings` so the
  lll/funlen/cyclop/dupl thresholds apply; fixed the resulting
  `goconst`, `dupl`, and `lll` findings; the informational `gomodguard`
  deprecation warning under this config is accepted
 - 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints,
  Makefile shims, README Entrypoints section
 - 2026-02-20: iterative DNS resolver implemented; tests made hermetic
  with mocked DNS (origin/feature/resolver, unmerged)
 - 2026-02-20: CI actions and go install refs pinned to commit SHAs;
  Gitea Actions workflow for make check (origin/ci/make-check, unmerged)
 - 2026-02-20: watcher monitoring orchestrator merged to main (#8)
 - 2026-02-20: DOMAINS/HOSTNAMES unified into single TARGETS config (#11)
 - 2026-02-19: TCP port connectivity checker, made concurrent with port
  validation; gosec G704 SSRF findings fixed without suppression
- 2026-02-19: TLS certificate inspector with no-peer-certificates error path and
+  (feature branches, unmerged)
-  IP SANs
+- 2026-02-19: TLS certificate inspector with no-peer-certificates error
  path and IP SANs (feature branch, unmerged)
 - 2026-02-19: gosec SSRF and formatting fixes on main
 - 2026-02-19: initial scaffold with per-nameserver DNS monitoring model
 # Future Steps
- nameserver IP address changes: https://git.eeqj.de/sneak/dnswatcher/issues/105
+Compliance:
- `DNSWATCHER_SENTRY_DSN` does nothing:
+
-  https://git.eeqj.de/sneak/dnswatcher/issues/107
+- Pin Dockerfile base images by sha256 and ensure the Docker build runs
- CORS on `/metrics`: https://git.eeqj.de/sneak/dnswatcher/issues/100
+  make check
- rate limit on `/metrics` Basic Auth:
+
-  https://git.eeqj.de/sneak/dnswatcher/issues/101
+Branch reconciliation:
- Dockerfile lint stage and `VERSION`:
+
-  https://git.eeqj.de/sneak/dnswatcher/issues/109
+- Sync local checkout with origin: local main is 8 commits behind
- trial run of the finished image:
+  origin/main; local feature/resolver has diverged from
-  https://git.eeqj.de/sneak/dnswatcher/issues/149
+  origin/feature/resolver, which already implements the resolver
- `goimports` in `make fmt-check`, Markdown formatting:
+- Merge in-flight branches to main once green: feature/resolver,
-  https://git.eeqj.de/sneak/dnswatcher/issues/119
+  ci/make-check, feature/portcheck-implementation,
- final state save at shutdown: https://git.eeqj.de/sneak/dnswatcher/issues/114
+  feature/tlscheck-implementation
- test-only constructors in `internal/state`:
+
-  https://git.eeqj.de/sneak/dnswatcher/issues/111
+Resolver (plan from untracked TODO.md; largely implemented on
- `internal/notify` shutdown tests:
+origin/feature/resolver, verify each item before closing):
-  https://git.eeqj.de/sneak/dnswatcher/issues/116
+
- README accuracy sweep: https://git.eeqj.de/sneak/dnswatcher/issues/108
+- Add github.com/miekg/dns dependency
- `script/install-precommit` in a linked worktree:
+- roots.go: hardcoded IANA root server list (a through m, IPv4/IPv6),
-  https://git.eeqj.de/sneak/dnswatcher/issues/129
+  rootServers() returning ip:53 strings
 - query.go: low-level query(ctx, server, name, qtype): UDP with TCP
  fallback on truncation, RD=0, context respected, 5s per-query timeout,
  returns raw *dns.Msg
 - trace.go: iterative delegation chasing from roots: referral detection
  (NOERROR, empty answer, NS in authority), glue extraction with
  bailiwick check, out-of-bailiwick NS resolved with recursion guard,
  delegation depth limit (20), retry across nameservers on failure, do
  not chase CNAMEs inside trace
 - FindAuthoritativeNameservers: NS set via trace, sorted, FQDN
  normalized, trailing dot handled; must pass its 9 tests
 - QueryNameserver: resolve NS host to IPs, query A/AAAA/CNAME/MX/TXT/
  SRV/CAA/NS, build NameserverResponse with status mapping (OK,
  NXDomain, NoData, Error), documented record formatting, sorted values,
  lame delegation detection; must pass its 16 tests
 - QueryAllNameservers: find NS set for parent domain (public suffix
  list), query all NS in parallel with bounded concurrency, return map
  even when all fail, context cancellation; must pass its 4 tests
 - LookupNS: thin wrapper over FindAuthoritativeNameservers, sorted,
  identical results; must pass its 3 tests
 - ResolveIPAddresses: collect A/AAAA from all NS, follow CNAME chains
  with MaxCNAMEDepth, dedupe, sort, NXDOMAIN returns empty slice with
  nil error; must pass its 9 tests
 - All 39 resolver tests pass, make check green, merge to main
 Watcher (internal/watcher/watcher.go):
 - Scheduling loop in Run(ctx): initial check on startup, separate
  tickers for DNS/port and TLS intervals, persist state via state.Save()
  after each cycle, clean shutdown on context cancel
 - Domain check: LookupNS, compare to stored state, store silently on
  first run, notify with old/new NS lists on change
 - Hostname check: QueryAllNameservers, compare per-NS records; notify on
  record changes, NS failure, NS recovery, inconsistency detected,
  inconsistency resolved, empty response; store silently on first run
 - Port check: ResolveIPAddresses, check ports 80 and 443 per IP, notify
  on open/closed transitions, handle new and disappeared IPs
 - TLS check: for each open IP:443, CheckCertificate; notify on expiry
  warning, certificate change (CN/issuer/SANs), TLS failure/recovery
 Port checker (internal/portcheck/portcheck.go):
 - Tests against known-open ports and RFC documentation IPs
 - CheckPort: net.DialTimeout (5s), context respected; (true, nil) open,
  (false, nil) closed/timeout/refused, error only for unexpected
  failures
 TLS checker (internal/tlscheck/tlscheck.go):
 - Tests against known public HTTPS servers, verify fields populated
 - CheckCertificate: tls.Dial to specific IP:443 with hostname as SNI;
  extract subject CN, issuer CN and org, NotAfter, SANs; error on
  handshake failure
 Notification service (internal/notify/notify.go, Slack/Mattermost/ntfy
 backends exist):
 - Structured notification types: DNS change, port change, TLS expiry,
  TLS change, NS failure, NS recovery, NS inconsistency
 - Per-backend formatting: Slack/Mattermost attachment colors (red
  failures/expiry, yellow warnings, green recoveries, blue info); ntfy
  priorities (urgent failures, high warnings, default changes, low
  recoveries); include hostname, nameserver, old/new values, timestamps
 HTTP API handlers:
 - Wire *state.State and *watcher.Watcher into handler params
 - GET /api/v1/status: full state snapshot as JSON
 - GET /api/v1/domains: domain states with NS records and last-checked
 - GET /api/v1/hostnames: hostname states with per-NS record data
 Infrastructure notes (from untracked TODO.md):
 - Module path sneak.berlin/go/dnswatcher differs from the git.eeqj.de
  remote intentionally; do not "fix" it
 - Dependencies: github.com/miekg/dns, golang.org/x/net/publicsuffix
 - Resolver tests originally used live DNS against *.dns.sneak.cloud
  (required records documented in the test file header); origin now has
  mocked hermetic tests, keep them hermetic
@@ -1,50 +0,0 @@
 package globals_test
 import (
 	"testing"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"sneak.berlin/go/dnswatcher/internal/globals"
 )
 // TestGlobals exercises the package-level version and appname
 // variables through their setters and read-back via New. These are
 // shared package state, so the test mutates a global and must run
 // sequentially; it cannot use t.Parallel().
 //
 //nolint:paralleltest // mutates shared package-level globals, must run sequentially
 func TestGlobals(t *testing.T) {
 	versions := []string{"v1.2.3", "dev", "", "v1.2.3-4-gabcdef"}
 	for _, want := range versions {
 		globals.SetVersion(want)
 		g, err := globals.New(nil)
 		require.NoError(t, err)
 		assert.Equal(t, want, g.Version,
 			"New must surface the version set by SetVersion")
 	}
 	names := []string{"dnswatcher", "other", ""}
 	for _, want := range names {
 		globals.SetAppname(want)
 		g, err := globals.New(nil)
 		require.NoError(t, err)
 		assert.Equal(t, want, g.Appname,
 			"New must surface the appname set by SetAppname")
 	}
 	// New returns a snapshot: a later SetVersion must not mutate a
 	// Globals handed out earlier.
 	globals.SetVersion("first")
 	g, err := globals.New(nil)
 	require.NoError(t, err)
 	globals.SetVersion("second")
 	assert.Equal(t, "first", g.Version,
 		"a Globals returned by New must not change when the "+
 			"package variable is set again")
 }
@@ -1,134 +0,0 @@
 package healthcheck_test
 import (
 	"context"
 	"encoding/json"
 	"testing"
 	"time"
 	"go.uber.org/fx"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"sneak.berlin/go/dnswatcher/internal/config"
 	"sneak.berlin/go/dnswatcher/internal/globals"
 	"sneak.berlin/go/dnswatcher/internal/healthcheck"
 	"sneak.berlin/go/dnswatcher/internal/logger"
 )
 // recordingLifecycle is a minimal fx.Lifecycle that records the hooks
 // appended to it, so healthcheck.New can be exercised through its real
 // constructor without standing up a whole fx application.
 type recordingLifecycle struct {
 	hooks []fx.Hook
 }
 func (l *recordingLifecycle) Append(hook fx.Hook) {
 	l.hooks = append(l.hooks, hook)
 }
 // newHealthcheck builds a Healthcheck through the real constructor and
 // runs the registered OnStart hook so StartupTime is set the same way
 // the fx lifecycle would set it.
 func newHealthcheck(
 	t *testing.T,
 	maintenance bool,
 	version string,
 ) *healthcheck.Healthcheck {
 	t.Helper()
 	g := &globals.Globals{Appname: "dnswatcher", Version: version}
 	log, err := logger.New(nil, logger.Params{Globals: g})
 	require.NoError(t, err)
 	lifecycle := &recordingLifecycle{}
 	hc, err := healthcheck.New(lifecycle, healthcheck.Params{
 		Globals: g,
 		Config:  &config.Config{MaintenanceMode: maintenance},
 		Logger:  log,
 	})
 	require.NoError(t, err)
 	require.Len(t, lifecycle.hooks, 1,
 		"New must register exactly one lifecycle hook")
 	require.NotNil(t, lifecycle.hooks[0].OnStart)
 	require.NoError(t, lifecycle.hooks[0].OnStart(context.Background()))
 	return hc
 }
 func TestCheckStatusAndPayloadShape(t *testing.T) {
 	t.Parallel()
 	hc := newHealthcheck(t, false, "v9.9.9")
 	resp := hc.Check()
 	assert.Equal(t, "ok", resp.Status)
 	// The JSON shape and field names are part of the contract for the
 	// /health and /.well-known/healthcheck routes, so assert on the
 	// exact set of keys the response marshals to.
 	raw, err := json.Marshal(resp)
 	require.NoError(t, err)
 	var fields map[string]json.RawMessage
 	require.NoError(t, json.Unmarshal(raw, &fields))
 	wantKeys := []string{
 		"status",
 		"now",
 		"uptimeSeconds",
 		"uptimeHuman",
 		"version",
 		"appname",
 		"maintenanceMode",
 	}
 	assert.Len(t, fields, len(wantKeys),
 		"response must marshal to exactly the documented fields")
 	for _, key := range wantKeys {
 		assert.Contains(t, fields, key, "missing JSON field %q", key)
 	}
 	// The Now field is documented as RFC3339Nano; a change to the
 	// format constant should turn this red.
 	_, err = time.Parse(time.RFC3339Nano, resp.Now)
 	assert.NoError(t, err, "Now must be RFC3339Nano")
 }
 func TestCheckMaintenanceModeReflectsConfig(t *testing.T) {
 	t.Parallel()
 	tests := []struct {
 		name        string
 		maintenance bool
 	}{
 		{"maintenance off", false},
 		{"maintenance on", true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 			hc := newHealthcheck(t, tt.maintenance, "test")
 			resp := hc.Check()
 			assert.Equal(t, tt.maintenance, resp.Maintenance,
 				"maintenanceMode must mirror Config.MaintenanceMode")
 		})
 	}
 }
 func TestCheckSurfacesVersionAndAppname(t *testing.T) {
 	t.Parallel()
 	hc := newHealthcheck(t, false, "surfaced-version-123")
 	resp := hc.Check()
 	assert.Equal(t, "surfaced-version-123", resp.Version,
 		"version from globals must appear in the payload")
 	assert.Equal(t, "dnswatcher", resp.Appname)
 }
@@ -1,121 +0,0 @@
 // Package livednstest runs the live DNS operations of tests. Tests that
 // look something up in DNS query live DNS servers, never a stand-in —
 // see TESTING.md. Nothing here mocks, fakes, stubs, records or replays
 // DNS, and nothing here skips a test: it only changes *how* the live
 // queries are issued, so that a single dropped UDP packet or one slow
 // authoritative server does not turn correct code into a red build.
 //
 // Two mechanisms:
 //
 //  1. Bounded concurrency. Tests run in parallel and the build hosts
 //     have many cores, so without a limit every test starts its own
 //     iterative resolution at the same instant and they all hit the
 //     first root server within a few milliseconds of each other. Root
 //     servers rate-limit that, which shows up as a different arbitrary
 //     subset of tests failing on each run. Run caps how many live
 //     operations are in flight at once in one test binary.
 //
 //  2. Retry with exponential backoff. Each live operation gets several
 //     attempts with its own timeout. An attempt is retried when it
 //     obtained nothing to check, never because of what the test
 //     asserts about the result, so a wrong result still fails on the
 //     first attempt. A fault in the code under test that leaves
 //     nothing to check looks the same as live DNS not answering, and
 //     fails only after the last attempt.
 package livednstest
 import (
 	"context"
 	"errors"
 	"testing"
 	"time"
 )
 const (
 	// attempts is how many times a live DNS operation is attempted
 	// before the test fails.
 	attempts = 3
 	// AttemptTimeout bounds one attempt. Worst case for an operation
 	// is attempts * AttemptTimeout plus the backoff — about 26
 	// seconds, well inside the 90-second `go test -timeout` backstop
 	// even when several operations exhaust their attempts.
 	AttemptTimeout = 8 * time.Second
 	// backoffBase is the delay after the first failed attempt; it is
 	// multiplied by backoffFactor each time.
 	backoffBase = 500 * time.Millisecond
 	// backoffFactor is the exponential backoff multiplier.
 	backoffFactor = 2
 	// Concurrency caps how many live operations may be in flight
 	// across one test binary at once.
 	Concurrency = 6
 )
 // gate bounds concurrent live operations. It has to be package scoped:
 // the whole point is that it is shared by every parallel test in the
 // test binary.
 //
 //nolint:gochecknoglobals // package-wide live query rate limit
 var gate = make(chan struct{}, Concurrency)
 // ErrNoAnswer reports that a live operation produced no usable answer,
 // which is retried rather than asserted on.
 var ErrNoAnswer = errors.New("no answer from live DNS")
 // Run executes one attempt of a live operation, holding a slot in gate
 // for its duration and bounding it with its own timeout.
 func Run(op func(ctx context.Context) error) error {
 	gate <- struct{}{}
 	defer func() { <-gate }()
 	ctx, cancel := context.WithTimeout(
 		context.Background(), AttemptTimeout,
 	)
 	defer cancel()
 	return op(ctx)
 }
 // Retry runs op until it reports success, retrying failures with
 // exponential backoff, and fails the test if every attempt fails. op
 // returns an error only for a failure to obtain an answer — never for
 // an answer the test disagrees with, which belongs in an assertion so
 // that it fails immediately. op stores whatever it obtained where its
 // caller can find it.
 func Retry(
 	t *testing.T,
 	what string,
 	op func(ctx context.Context) error,
 ) {
 	t.Helper()
 	var last error
 	backoff := backoffBase
 	for attempt := range attempts {
 		if attempt > 0 {
 			t.Logf(
 				"%s: attempt %d of %d failed (%v), "+
 					"retrying in %s",
 				what, attempt, attempts, last, backoff,
 			)
 			time.Sleep(backoff)
 			backoff *= backoffFactor
 		}
 		last = Run(op)
 		if last == nil {
 			return
 		}
 	}
 	t.Fatalf(
 		"%s: all %d live attempts failed: %v",
 		what, attempts, last,
 	)
 }
@@ -1,103 +0,0 @@
 package livednstest_test
 import (
 	"context"
 	"sync"
 	"testing"
 	"time"
 	"github.com/stretchr/testify/assert"
 	"sneak.berlin/go/dnswatcher/internal/livednstest"
 )
 // Tests for the retry and the concurrency limit themselves. They
 // perform no DNS resolution of any kind.
 func TestRetryRecoversFromTransientFailure(t *testing.T) {
 	t.Parallel()
 	const wantAttempts = 2
 	attempts := 0
 	livednstest.Retry(t, "transient", func(_ context.Context) error {
 		attempts++
 		if attempts < wantAttempts {
 			return livednstest.ErrNoAnswer
 		}
 		return nil
 	})
 	assert.Equal(t, wantAttempts, attempts)
 }
 func TestRetryGivesEachAttemptADeadline(t *testing.T) {
 	t.Parallel()
 	livednstest.Retry(t, "deadline", func(ctx context.Context) error {
 		deadline, ok := ctx.Deadline()
 		assert.True(t, ok, "attempt should carry a deadline")
 		remaining := time.Until(deadline)
 		assert.LessOrEqual(t, remaining, livednstest.AttemptTimeout)
 		// Lower bound too: without one this passes for a
 		// deadline far shorter than intended, which would
 		// silently turn every live attempt into an instant
 		// timeout.
 		assert.Greater(t, remaining, livednstest.AttemptTimeout/2)
 		return nil
 	})
 }
 func TestRunBoundsConcurrency(t *testing.T) {
 	t.Parallel()
 	const workers = 24
 	var (
 		mu       sync.Mutex
 		wg       sync.WaitGroup
 		inFlight int
 		maxSeen  int
 	)
 	wg.Add(workers)
 	for range workers {
 		go func() {
 			defer wg.Done()
 			_ = livednstest.Run(func(_ context.Context) error {
 				mu.Lock()
 				inFlight++
 				if inFlight > maxSeen {
 					maxSeen = inFlight
 				}
 				mu.Unlock()
 				time.Sleep(time.Millisecond)
 				mu.Lock()
 				inFlight--
 				mu.Unlock()
 				return nil
 			})
 		}()
 	}
 	wg.Wait()
 	assert.Positive(t, maxSeen)
 	assert.LessOrEqual(
 		t, maxSeen, livednstest.Concurrency,
 		"live queries must stay under the package-wide gate",
 	)
 }
@@ -1,66 +0,0 @@
 package logger_test
 import (
 	"context"
 	"log/slog"
 	"testing"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"sneak.berlin/go/dnswatcher/internal/globals"
 	"sneak.berlin/go/dnswatcher/internal/logger"
 )
 func newTestLogger(t *testing.T) *logger.Logger {
 	t.Helper()
 	g := &globals.Globals{Appname: "dnswatcher", Version: "test"}
 	l, err := logger.New(nil, logger.Params{Globals: g})
 	require.NoError(t, err)
 	return l
 }
 // TestNewReturnsUsableLogger checks that the constructor yields a
 // working *slog.Logger.
 func TestNewReturnsUsableLogger(t *testing.T) {
 	t.Parallel()
 	l := newTestLogger(t)
 	require.NotNil(t, l.Get(), "Get must return a non-nil logger")
 }
 // TestDefaultLevelExcludesDebug verifies the default configuration
 // logs at info: debug records are suppressed, info records pass.
 func TestDefaultLevelExcludesDebug(t *testing.T) {
 	t.Parallel()
 	log := newTestLogger(t).Get()
 	ctx := context.Background()
 	assert.False(t, log.Enabled(ctx, slog.LevelDebug),
 		"debug must be suppressed at the default level")
 	assert.True(t, log.Enabled(ctx, slog.LevelInfo),
 		"info must be enabled at the default level")
 }
 // TestEnableDebugLoggingChangesLevel verifies the debug and non-debug
 // configurations differ as intended: enabling debug makes debug
 // records pass where they previously did not.
 func TestEnableDebugLoggingChangesLevel(t *testing.T) {
 	t.Parallel()
 	l := newTestLogger(t)
 	log := l.Get()
 	ctx := context.Background()
 	require.False(t, log.Enabled(ctx, slog.LevelDebug),
 		"debug must start disabled")
 	l.EnableDebugLogging()
 	assert.True(t, log.Enabled(ctx, slog.LevelDebug),
 		"debug must be enabled after EnableDebugLogging")
 }
@@ -7,8 +7,8 @@ import (
 	"github.com/miekg/dns"
 )
-// DNSClient sends one DNS message to a nameserver and returns the
+// DNSClient abstracts DNS wire-protocol exchanges so the resolver
-// reply. The resolver holds one for UDP and one for TCP.
+// can be tested without hitting real nameservers.
 type DNSClient interface {
 	ExchangeContext(
 		ctx context.Context,
@@ -1,8 +0,0 @@
 package resolver
 import "github.com/miekg/dns"
 // ExtractRecordValue exports extractRecordValue for testing.
 func ExtractRecordValue(rr dns.RR) string {
 	return extractRecordValue(rr)
 }
@@ -608,10 +608,7 @@ func classifyResponse(resp *NameserverResponse, state queryState) {
 	}
 }
-// extractRecordValue formats a DNS RR value as a string. DNS names
+// extractRecordValue formats a DNS RR value as a string.
 // are case-insensitive and nameservers may answer in any letter case,
 // so names are lower-cased to compare equal. TXT and CAA values keep
 // their letter case.
 func extractRecordValue(rr dns.RR) string {
 	switch r := rr.(type) {
 	case *dns.A:
@@ -619,22 +616,22 @@ func extractRecordValue(rr dns.RR) string {
 	case *dns.AAAA:
 		return r.AAAA.String()
 	case *dns.CNAME:
-		return strings.ToLower(r.Target)
+		return r.Target
 	case *dns.MX:
-		return fmt.Sprintf("%d %s", r.Preference, strings.ToLower(r.Mx))
+		return fmt.Sprintf("%d %s", r.Preference, r.Mx)
 	case *dns.TXT:
 		return strings.Join(r.Txt, "")
 	case *dns.SRV:
 		return fmt.Sprintf(
 			"%d %d %d %s",
-			r.Priority, r.Weight, r.Port, strings.ToLower(r.Target),
+			r.Priority, r.Weight, r.Port, r.Target,
 		)
 	case *dns.CAA:
 		return fmt.Sprintf(
 			"%d %s \"%s\"", r.Flag, r.Tag, r.Value,
 		)
 	case *dns.NS:
-		return strings.ToLower(r.Ns)
+		return r.Ns
 	default:
 		return ""
 	}
@@ -1,62 +0,0 @@
 package resolver_test
 import (
 	"testing"
 	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 	"sneak.berlin/go/dnswatcher/internal/resolver"
 )
 func TestExtractRecordValue_LetterCase(t *testing.T) {
 	t.Parallel()
 	tests := []struct {
 		name string
 		rr   dns.RR
 		want string
 	}{
 		{
 			name: "MX target lower-cased",
 			rr:   &dns.MX{Preference: 1, Mx: "ASPMX.L.GOOGLE.COM."},
 			want: "1 aspmx.l.google.com.",
 		},
 		{
 			name: "NS target lower-cased",
 			rr:   &dns.NS{Ns: "x.ns.joker.COM."},
 			want: "x.ns.joker.com.",
 		},
 		{
 			name: "CNAME target lower-cased",
 			rr:   &dns.CNAME{Target: "WWW.Example.Com."},
 			want: "www.example.com.",
 		},
 		{
 			name: "SRV target lower-cased",
 			rr: &dns.SRV{
 				Priority: 10, Weight: 5, Port: 443,
 				Target: "SIP.Example.Com.",
 			},
 			want: "10 5 443 sip.example.com.",
 		},
 		{
 			name: "TXT value keeps its case",
 			rr:   &dns.TXT{Txt: []string{"Verify=AbC123"}},
 			want: "Verify=AbC123",
 		},
 		{
 			name: "CAA value keeps its case",
 			rr:   &dns.CAA{Flag: 0, Tag: "issue", Value: "LetsEncrypt.org"},
 			want: `0 issue "LetsEncrypt.org"`,
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 			assert.Equal(t, tt.want, resolver.ExtractRecordValue(tt.rr))
 		})
 	}
 }
@@ -1,7 +1,10 @@
 package resolver_test
 import (
 	"context"
 	"sync"
 	"testing"
 	"time"
 	"github.com/stretchr/testify/assert"
@@ -9,8 +12,9 @@ import (
 )
 // Tests for the live-DNS harness in livedns_test.go itself. These
-// exercise pure logic; they perform no DNS resolution of any kind, so
+// exercise pure logic and the retry/concurrency plumbing; they
-// they neither mock DNS nor depend on it.
+// perform no DNS resolution of any kind, so they neither mock DNS
 // nor depend on it.
 // Names for the synthetic status maps below. Nothing is ever queried
 // at them: they are map keys handed to the package's pure counting
@@ -86,6 +90,47 @@ func TestStatusCountingIgnoresSilentNameservers(t *testing.T) {
 	)
 }
 func TestRetryLiveRecoversFromTransientFailure(t *testing.T) {
 	t.Parallel()
 	const wantAttempts = 2
 	attempts := 0
 	retryLive(t, "transient", func(_ context.Context) error {
 		attempts++
 		if attempts < wantAttempts {
 			return errLiveNoAnswer
 		}
 		return nil
 	})
 	assert.Equal(t, wantAttempts, attempts)
 }
 func TestRetryLiveGivesEachAttemptADeadline(t *testing.T) {
 	t.Parallel()
 	retryLive(t, "deadline", func(ctx context.Context) error {
 		deadline, ok := ctx.Deadline()
 		assert.True(t, ok, "attempt should carry a deadline")
 		remaining := time.Until(deadline)
 		assert.LessOrEqual(t, remaining, liveAttemptTimeout)
 		// Lower bound too: without one this passes for a
 		// deadline far shorter than intended, which would
 		// silently turn every live attempt into an instant
 		// timeout.
 		assert.Greater(t, remaining, liveAttemptTimeout/2)
 		return nil
 	})
 }
 // TestUnsanctionedStatusesRejectsWrongAnswers is the regression test
 // for the defect this allowlist exists to prevent: a minority of
 // nameservers answering WRONGLY while quorum keeps the suite green.
@@ -190,3 +235,50 @@ func TestUnsanctionedStatusesToleratesSilenceOnly(t *testing.T) {
 		unsanctionedStatuses(results, allowed...),
 	)
 }
 func TestRunLiveBoundsConcurrency(t *testing.T) {
 	t.Parallel()
 	const workers = 24
 	var (
 		mu       sync.Mutex
 		wg       sync.WaitGroup
 		inFlight int
 		maxSeen  int
 	)
 	wg.Add(workers)
 	for range workers {
 		go func() {
 			defer wg.Done()
 			_ = runLive(func(_ context.Context) error {
 				mu.Lock()
 				inFlight++
 				if inFlight > maxSeen {
 					maxSeen = inFlight
 				}
 				mu.Unlock()
 				time.Sleep(time.Millisecond)
 				mu.Lock()
 				inFlight--
 				mu.Unlock()
 				return nil
 			})
 		}()
 	}
 	wg.Wait()
 	assert.Positive(t, maxSeen)
 	assert.LessOrEqual(
 		t, maxSeen, liveConcurrency,
 		"live queries must stay under the package-wide gate",
 	)
 }
@@ -8,8 +8,8 @@ import (
 	"sort"
 	"strings"
 	"testing"
 	"time"
 	"sneak.berlin/go/dnswatcher/internal/livednstest"
 	"sneak.berlin/go/dnswatcher/internal/resolver"
 )
@@ -17,34 +17,144 @@ import (
 // Live DNS test support
 // ----------------------------------------------------------------
 //
-// Tests that look something up in DNS query live DNS servers, never a
+// Every test in this package resolves against the real, live DNS —
-// stand-in; logic that works on record data may be tested on that
+// see TESTING.md. Nothing here mocks, fakes, stubs, records or
-// data with no lookup (see TESTING.md). Each live operation below goes
+// replays DNS, and nothing here skips or gates a test: the helpers
-// through livednstest.Retry, which bounds how many resolutions are in
+// below only change *how* the live queries are issued, so that a
-// flight at once and retries an operation that got no answer (see
+// single dropped UDP packet or one slow authoritative server does
-// package livednstest).
+// not turn a correct resolver into a red build.
 //
-// Where an assertion spans several independent nameservers, a quorum
+// Three mechanisms, all test-side:
 // is enough: a strict majority answering as expected. A server that
 // fails to answer is tolerated, while a server that answers *wrongly*
 // still fails the test.
 //
-// That tolerance is expressed as an ALLOWLIST of sanctioned statuses,
+//  1. Bounded concurrency. The package's tests are parallel and the
-// never as a blocklist of known-bad ones. A blocklist bans the one
+//     build hosts have many cores, so without a limit every test
-// wrong answer its author thought of and silently admits every other
+//     starts its own iterative resolution at the same instant and
-// status, including any added to the resolver later; an allowlist
+//     they all hit the first root server in rootServerList() within
-// fails on anything nobody explicitly sanctioned. Silence (timeout,
+//     a few milliseconds of each other. Root servers rate-limit
-// error) is the only thing quorum exists to tolerate. A *wrong
+//     that, which shows up as a different arbitrary subset of tests
-// answer* — nxdomain for a name that exists, ok for one that does
+//     failing on each run. liveGate caps how many resolutions are
-// not, nodata for either — is never tolerated at any count.
+//     in flight at once.
 //
 //  2. Retry with exponential backoff. Each live operation gets
 //     several attempts with its own timeout. The retry predicate is
 //     strictly transport-level — "did a nameserver answer at all" —
 //     never the assertion the test is making. A resolver that
 //     answers incorrectly still fails on the first attempt.
 //
 //  3. Quorum. Where an assertion spans several independent
 //     nameservers, a strict majority answering as expected is
 //     enough; a server that fails to answer is tolerated, while a
 //     server that answers *wrongly* still fails the test.
 //
 // The tolerance in (3) is expressed as an ALLOWLIST of sanctioned
 // statuses, never as a blocklist of known-bad ones. A blocklist bans
 // the one wrong answer its author thought of and silently admits
 // every other status, including any added to the resolver later; an
 // allowlist fails on anything nobody explicitly sanctioned. Silence
 // (timeout, error) is the only thing quorum exists to tolerate. A
 // *wrong answer* — nxdomain for a name that exists, ok for one that
 // does not, nodata for either — is never tolerated at any count.
-// minNameservers is the smallest nameserver count a well-run zone is
+const (
-// expected to publish.
+	// liveAttempts is how many times a live DNS operation is
-const minNameservers = 2
+	// attempted before the test fails.
 	liveAttempts = 3
-// errLiveNoQuorum reports that too few of a domain's nameservers
+	// liveAttemptTimeout bounds one attempt. Worst case for an
-// answered for a quorum assertion to be made.
+	// operation is liveAttempts * liveAttemptTimeout plus the
-var errLiveNoQuorum = errors.New("no nameserver quorum")
+	// backoff — about 26 seconds, well inside the 90-second
 	// `go test -timeout` backstop even when several operations
 	// exhaust their attempts.
 	liveAttemptTimeout = 8 * time.Second
 	// liveBackoffBase is the delay after the first failed
 	// attempt; it is multiplied by liveBackoffFactor each time.
 	liveBackoffBase = 500 * time.Millisecond
 	// liveBackoffFactor is the exponential backoff multiplier.
 	liveBackoffFactor = 2
 	// liveConcurrency caps how many live resolutions may be in
 	// flight across the whole package at once.
 	liveConcurrency = 6
 	// minNameservers is the smallest nameserver count a
 	// well-run zone is expected to publish.
 	minNameservers = 2
 )
 // liveGate bounds concurrent live resolutions package-wide. It has
 // to be package scoped: the whole point is that it is shared by
 // every parallel test in the package.
 //
 //nolint:gochecknoglobals // package-wide live query rate limit
 var liveGate = make(chan struct{}, liveConcurrency)
 var (
 	// errLiveNoAnswer reports that a live operation produced no
 	// usable answer, which is retried rather than asserted on.
 	errLiveNoAnswer = errors.New("no answer from live DNS")
 	// errLiveNoQuorum reports that too few of a domain's
 	// nameservers answered for a quorum assertion to be made.
 	errLiveNoQuorum = errors.New("no nameserver quorum")
 )
 // runLive executes one attempt of a live operation, holding a slot
 // in liveGate for its duration and bounding it with its own
 // timeout.
 func runLive(op func(ctx context.Context) error) error {
 	liveGate <- struct{}{}
 	defer func() { <-liveGate }()
 	ctx, cancel := context.WithTimeout(
 		context.Background(), liveAttemptTimeout,
 	)
 	defer cancel()
 	return op(ctx)
 }
 // retryLive runs op until it reports success, retrying transport
 // failures with exponential backoff, and fails the test if every
 // attempt fails. op returns an error only for a failure to obtain
 // an answer — never for an answer the test disagrees with, which
 // belongs in an assertion so that it fails immediately. op stores
 // whatever it obtained where its caller can find it.
 func retryLive(
 	t *testing.T,
 	what string,
 	op func(ctx context.Context) error,
 ) {
 	t.Helper()
 	var last error
 	backoff := liveBackoffBase
 	for attempt := range liveAttempts {
 		if attempt > 0 {
 			t.Logf(
 				"%s: attempt %d of %d failed (%v), "+
 					"retrying in %s",
 				what, attempt, liveAttempts, last, backoff,
 			)
 			time.Sleep(backoff)
 			backoff *= liveBackoffFactor
 		}
 		last = runLive(op)
 		if last == nil {
 			return
 		}
 	}
 	t.Fatalf(
 		"%s: no answer after %d live attempts: %v",
 		what, liveAttempts, last,
 	)
 }
 // liveQuorum is how many of total nameservers must agree for a
 // multi-nameserver assertion to hold: a strict majority.
@@ -162,7 +272,7 @@ func liveFindAuthoritative(
 	var out []string
-	livednstest.Retry(
+	retryLive(
 		t,
 		"FindAuthoritativeNameservers("+domain+")",
 		func(ctx context.Context) error {
@@ -174,7 +284,7 @@ func liveFindAuthoritative(
 			if len(ns) == 0 {
 				return fmt.Errorf(
 					"%w: %s has no nameservers",
-					livednstest.ErrNoAnswer, domain,
+					errLiveNoAnswer, domain,
 				)
 			}
@@ -198,7 +308,7 @@ func liveLookupNS(
 	var out []string
-	livednstest.Retry(
+	retryLive(
 		t,
 		"LookupNS("+domain+")",
 		func(ctx context.Context) error {
@@ -210,7 +320,7 @@ func liveLookupNS(
 			if len(ns) == 0 {
 				return fmt.Errorf(
 					"%w: %s has no nameservers",
-					livednstest.ErrNoAnswer, domain,
+					errLiveNoAnswer, domain,
 				)
 			}
@@ -240,7 +350,7 @@ func liveQueryNameserver(
 	var out *resolver.NameserverResponse
-	livednstest.Retry(
+	retryLive(
 		t,
 		what,
 		func(ctx context.Context) error {
@@ -255,7 +365,7 @@ func liveQueryNameserver(
 				resp.Status == resolver.StatusError {
 				return fmt.Errorf(
 					"%w: %s returned %s: %s",
-					livednstest.ErrNoAnswer, nameserver,
+					errLiveNoAnswer, nameserver,
 					resp.Status, resp.Error,
 				)
 			}
@@ -282,7 +392,7 @@ func liveQueryAllNameservers(
 	var out map[string]*resolver.NameserverResponse
-	livednstest.Retry(
+	retryLive(
 		t,
 		"QueryAllNameservers("+hostname+")",
 		func(ctx context.Context) error {
@@ -294,7 +404,7 @@ func liveQueryAllNameservers(
 			if len(results) == 0 {
 				return fmt.Errorf(
 					"%w: no nameservers queried for %s",
-					livednstest.ErrNoAnswer, hostname,
+					errLiveNoAnswer, hostname,
 				)
 			}
@@ -327,7 +437,7 @@ func liveResolveIPs(
 	var out []string
-	livednstest.Retry(
+	retryLive(
 		t,
 		"ResolveIPAddresses("+hostname+")",
 		func(ctx context.Context) error {
@@ -339,7 +449,7 @@ func liveResolveIPs(
 			if len(ips) == 0 {
 				return fmt.Errorf(
 					"%w: no addresses for %s",
-					livednstest.ErrNoAnswer, hostname,
+					errLiveNoAnswer, hostname,
 				)
 			}
@@ -366,7 +476,7 @@ func liveResolveIPsAllowingEmpty(
 	var out []string
-	livednstest.Retry(
+	retryLive(
 		t,
 		"ResolveIPAddresses("+hostname+")",
 		func(ctx context.Context) error {
@@ -67,4 +67,17 @@ func NewFromLogger(log *slog.Logger) *Resolver {
 	}
 }
 // NewFromLoggerWithClient creates a Resolver with a custom DNS
 // client, useful for testing with mock DNS responses.
 func NewFromLoggerWithClient(
 	log *slog.Logger,
 	client DNSClient,
 ) *Resolver {
 	return &Resolver{
 		log:    log,
 		client: client,
 		tcp:    client,
 	}
 }
 // Method implementations are in iterative.go.
@@ -10,6 +10,7 @@ import (
 	"testing"
 	"time"
 	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -32,8 +33,8 @@ func newTestResolver(t *testing.T) *resolver.Resolver {
 }
 // findOneNSForDomain picks one authoritative nameserver to aim a
-// test at. Quorum handling lives in livedns_test.go, and the live-DNS
+// test at. Live-DNS retry, concurrency and quorum handling live in
-// retry and concurrency limit in package livednstest.
+// livedns_test.go.
 func findOneNSForDomain(
 	t *testing.T,
 	r *resolver.Resolver,
@@ -525,18 +526,21 @@ func TestQueryAllNameservers_ContextCanceled(t *testing.T) {
 func TestQueryNameserverIP_Timeout(t *testing.T) {
 	t.Parallel()
-	r := newTestResolver(t)
+	log := slog.New(slog.NewTextHandler(
 		os.Stderr,
 		&slog.HandlerOptions{Level: slog.LevelDebug},
 	))
 	r := resolver.NewFromLoggerWithClient(
 		log, &timeoutClient{},
 	)
 	// Nothing answers at 192.0.2.1, a documentation address. The
 	// resolver tries each query twice, and the first try gives up
 	// after two seconds. A deadline that ends during the first try
 	// makes the status vary from run to run between nodata and
 	// timeout, so the deadline must outlast the first try.
 	ctx, cancel := context.WithTimeout(
-		context.Background(), 3*time.Second,
+		context.Background(), 10*time.Second,
 	)
 	t.Cleanup(cancel)
 	// Query any IP — the client always returns a timeout error.
 	resp, err := r.QueryNameserverIP(
 		ctx, "unreachable.test.", "192.0.2.1",
 		"example.com",
@@ -547,6 +551,27 @@ func TestQueryNameserverIP_Timeout(t *testing.T) {
 	assert.NotEmpty(t, resp.Error)
 }
 // timeoutClient simulates DNS timeout errors for testing.
 type timeoutClient struct{}
 func (c *timeoutClient) ExchangeContext(
 	_ context.Context,
 	_ *dns.Msg,
 	_ string,
 ) (*dns.Msg, time.Duration, error) {
 	return nil, 0, &net.OpError{
 		Op:  "read",
 		Net: "udp",
 		Err: &timeoutError{},
 	}
 }
 type timeoutError struct{}
 func (e *timeoutError) Error() string   { return "i/o timeout" }
 func (e *timeoutError) Timeout() bool   { return true }
 func (e *timeoutError) Temporary() bool { return true }
 func TestResolveIPAddresses_ContextCanceled(t *testing.T) {
 	t.Parallel()
@@ -5,20 +5,15 @@ import (
 	"time"
 )
 // NewHTTPServer exports newHTTPServer for testing.
 func NewHTTPServer(
 	listenAddr string,
 	handler http.Handler,
 ) *http.Server {
 	return newHTTPServer(listenAddr, handler)
 }
 // RequestTimeout exports the handler execution budget applied by
 // chimw.Timeout in SetupRoutes, so tests can assert the relationship
 // between it and the server's WriteTimeout.
 const RequestTimeout time.Duration = requestTimeout
 // SetListenPort overrides the port Run binds. A test uses it to hand
 // Run an unbindable port so ListenAndServe fails immediately and Run
 // returns after storing its http.Server.
 func SetListenPort(s *Server, port int) {
 	s.port = port
 }
 // HTTPServerOf returns the http.Server that Run built and stored, so a
 // test can inspect the timeouts the running server actually carries.
 func HTTPServerOf(s *Server) *http.Server {
 	return s.httpServer
 }
@@ -1,130 +1,112 @@
 package server_test
 import (
 	"net/http"
 	"testing"
 	"github.com/spf13/viper"
 	"go.uber.org/fx"
 	"sneak.berlin/go/dnswatcher/internal/config"
 	"sneak.berlin/go/dnswatcher/internal/globals"
 	"sneak.berlin/go/dnswatcher/internal/handlers"
 	"sneak.berlin/go/dnswatcher/internal/healthcheck"
 	"sneak.berlin/go/dnswatcher/internal/logger"
 	"sneak.berlin/go/dnswatcher/internal/middleware"
 	"sneak.berlin/go/dnswatcher/internal/notify"
 	"sneak.berlin/go/dnswatcher/internal/server"
 	"sneak.berlin/go/dnswatcher/internal/state"
 )
-// buildServer wires a *server.Server exactly as cmd/dnswatcher does,
+// noopHandler stands in for the router; newHTTPServer only stores it.
-// minus the watcher/resolver subtree that would touch live DNS. fx
+func noopHandler() http.Handler {
-// builds the object graph but the lifecycle is never started, so no
+	return http.HandlerFunc(
-// OnStart hook runs and nothing listens or resolves. The caller must
+		func(w http.ResponseWriter, _ *http.Request) {
-// first configure viper (config.New reads it), which is also why the
+			w.WriteHeader(http.StatusOK)
-// caller cannot run in parallel.
+		},
 func buildServer(t *testing.T) *server.Server {
 	t.Helper()
 	var srv *server.Server
 	app := fx.New(
 		fx.NopLogger,
 		fx.Provide(
 			globals.New,
 			logger.New,
 			config.New,
 			state.New,
 			healthcheck.New,
 			notify.New,
 			middleware.New,
 			handlers.New,
 			server.New,
 		),
 		fx.Populate(&srv),
 	)
 	err := app.Err()
 	if err != nil {
 		t.Fatalf("building server graph: %v", err)
 	}
 	return srv
 }
-// TestRunWiresSocketTimeouts pins that the http.Server the running
+// TestHTTPServerTimeoutsAreSet asserts that every socket-level
-// server actually serves — the one Run builds and hands to
+// timeout is configured. A zero value in net/http means "no limit",
-// ListenAndServe — carries every socket-level timeout, plus the two
+// so a refactor that silently drops one of these reintroduces the
-// relationships the values must satisfy.
+// slowloris / unreaped-keep-alive exposure this guards against.
 //
-// Run is driven to completion with an unbindable port: it builds and
+// The assertions are on the configured field values only; nothing
-// stores s.httpServer, then ListenAndServe fails at once and Run
+// here measures elapsed time, so the test cannot flake on timing.
-// returns without ever listening. The assertions run in the same
+func TestHTTPServerTimeoutsAreSet(t *testing.T) {
-// goroutine after Run returns, so reading s.httpServer is free of any
+	t.Parallel()
 // data race. Nothing here measures elapsed time.
 //
 // ReadTimeout must be at least ReadHeaderTimeout. net/http reads the
 // headers under ReadHeaderTimeout, then sets the read deadline for the
 // rest of the request to ReadTimeout, counted from when it started
 // reading the request. If ReadTimeout were smaller, a request whose
 // headers arrived after ReadTimeout but within ReadHeaderTimeout would
 // get a read deadline that had already passed, so reading its body
 // would fail at once.
 func TestRunWiresSocketTimeouts(t *testing.T) {
 	// Sets an env var and touches viper global state, so like the
 	// config tests it cannot use t.Parallel.
 	viper.Reset()
 	t.Setenv("DNSWATCHER_TARGETS", "example.com")
-	srv := buildServer(t)
+	srv := server.NewHTTPServer(":8080", noopHandler())
 	server.SetListenPort(srv, -1)
-	srv.Run()
+	if srv.ReadTimeout <= 0 {
 	hs := server.HTTPServerOf(srv)
 	if hs == nil {
 		t.Fatal("Run did not build an http.Server")
 	}
 	if hs.ReadTimeout <= 0 {
 		t.Errorf("ReadTimeout must be non-zero, got %v", hs.ReadTimeout)
 	}
 	if hs.ReadHeaderTimeout <= 0 {
 		t.Errorf(
-			"ReadHeaderTimeout must be non-zero, got %v",
+			"ReadTimeout must be non-zero, got %v",
-			hs.ReadHeaderTimeout,
+			srv.ReadTimeout,
 		)
 	}
-	if hs.WriteTimeout <= 0 {
+	if srv.ReadHeaderTimeout <= 0 {
-		t.Errorf("WriteTimeout must be non-zero, got %v", hs.WriteTimeout)
+		t.Errorf(
 			"ReadHeaderTimeout must be non-zero, got %v",
 			srv.ReadHeaderTimeout,
 		)
 	}
-	if hs.IdleTimeout <= 0 {
+	if srv.WriteTimeout <= 0 {
-		t.Errorf("IdleTimeout must be non-zero, got %v", hs.IdleTimeout)
+		t.Errorf(
 			"WriteTimeout must be non-zero, got %v",
 			srv.WriteTimeout,
 		)
 	}
-	if hs.WriteTimeout <= server.RequestTimeout {
+	if srv.IdleTimeout <= 0 {
 		t.Errorf(
 			"IdleTimeout must be non-zero, got %v",
 			srv.IdleTimeout,
 		)
 	}
 }
 // TestWriteTimeoutExceedsHandlerBudget pins the one relationship the
 // values must satisfy. net/http arms the write deadline once request
 // headers are read, so it covers handler execution plus the response
 // flush. If WriteTimeout were not greater than the chimw.Timeout
 // handler budget, the connection would be severed before a handler
 // that used its full budget could respond, making that budget
 // unreachable.
 func TestWriteTimeoutExceedsHandlerBudget(t *testing.T) {
 	t.Parallel()
 	srv := server.NewHTTPServer(":8080", noopHandler())
 	if srv.WriteTimeout <= server.RequestTimeout {
 		t.Errorf(
 			"WriteTimeout (%v) must exceed handler budget (%v)",
-			hs.WriteTimeout,
+			srv.WriteTimeout,
 			server.RequestTimeout,
 		)
 	}
 }
-	if hs.ReadTimeout < hs.ReadHeaderTimeout {
+// TestReadTimeoutCoversHeaderTimeout asserts the read deadline for
 // the whole request is at least as long as the header-only deadline;
 // a smaller ReadTimeout would make ReadHeaderTimeout unreachable.
 func TestReadTimeoutCoversHeaderTimeout(t *testing.T) {
 	t.Parallel()
 	srv := server.NewHTTPServer(":8080", noopHandler())
 	if srv.ReadTimeout < srv.ReadHeaderTimeout {
 		t.Errorf(
 			"ReadTimeout (%v) must be >= ReadHeaderTimeout (%v)",
-			hs.ReadTimeout,
+			srv.ReadTimeout,
-			hs.ReadHeaderTimeout,
+			srv.ReadHeaderTimeout,
 		)
 	}
 	if hs.Handler != srv {
 		t.Errorf(
 			"Run wired handler %T, want the *server.Server",
 			hs.Handler,
 		)
 	}
 }
 // TestHTTPServerAddrAndHandler covers the rest of the constructor so
 // a future edit cannot drop the listen address or the handler.
 func TestHTTPServerAddrAndHandler(t *testing.T) {
 	t.Parallel()
 	srv := server.NewHTTPServer(":9999", noopHandler())
 	if srv.Addr != ":9999" {
 		t.Errorf("Addr = %q, want %q", srv.Addr, ":9999")
 	}
 	if srv.Handler == nil {
 		t.Error("Handler must not be nil")
 	}
 }
@@ -148,11 +148,6 @@ func New(
 	lifecycle.Append(fx.Hook{
 		OnStart: func(_ context.Context) error {
 			err := state.checkDataDirWritable()
 			if err != nil {
 				return err
 			}
 			return state.Load()
 		},
 		OnStop: func(_ context.Context) error {
@@ -350,27 +345,3 @@ func (s *State) GetCertificateState(
 	return cs, ok
 }
 // checkDataDirWritable creates the data directory if needed, then writes
 // and removes the temp file that Save uses. It runs at startup so that an
 // unwritable directory stops the process, instead of the process running
 // with every save failing and only logged.
 func (s *State) checkDataDirWritable() error {
 	dir := s.config.DataDir
 	tmpPath := s.config.StatePath() + ".tmp"
 	err := os.MkdirAll(dir, dirPermissions)
 	if err == nil {
 		err = os.WriteFile(tmpPath, nil, filePermissions)
 	}
 	if err == nil {
 		err = os.Remove(tmpPath)
 	}
 	if err != nil {
 		return fmt.Errorf("data directory %s is not writable: %w", dir, err)
 	}
 	return nil
 }
@@ -4,16 +4,10 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
 	"strings"
 	"sync"
 	"testing"
 	"time"
 	"go.uber.org/fx/fxtest"
 	"sneak.berlin/go/dnswatcher/internal/config"
 	"sneak.berlin/go/dnswatcher/internal/globals"
 	"sneak.berlin/go/dnswatcher/internal/logger"
 	"sneak.berlin/go/dnswatcher/internal/state"
 )
@@ -499,107 +493,6 @@ func TestSaveWritePermissionError(t *testing.T) {
 	}
 }
 // startState builds a State through the real constructor and runs its
 // startup hook against dataDir, returning the startup error.
 func startState(t *testing.T, dataDir string) error {
 	t.Helper()
 	g, err := globals.New(nil)
 	if err != nil {
 		t.Fatalf("globals.New: %v", err)
 	}
 	log, err := logger.New(nil, logger.Params{Globals: g})
 	if err != nil {
 		t.Fatalf("logger.New: %v", err)
 	}
 	lifecycle := fxtest.NewLifecycle(t)
 	_, err = state.New(lifecycle, state.Params{
 		Logger: log,
 		Config: &config.Config{DataDir: dataDir},
 	})
 	if err != nil {
 		t.Fatalf("state.New: %v", err)
 	}
 	return lifecycle.Start(t.Context())
 }
 // TestStartupFailsWhenDataDirNotWritable verifies that startup stops
 // with an error naming the data directory when it cannot be written.
 // The directory's parent is a regular file, which also fails as root.
 func TestStartupFailsWhenDataDirNotWritable(t *testing.T) {
 	t.Parallel()
 	parent := filepath.Join(t.TempDir(), "file")
 	err := os.WriteFile(parent, nil, 0o600)
 	if err != nil {
 		t.Fatalf("writing file: %v", err)
 	}
 	dataDir := filepath.Join(parent, "data")
 	err = startState(t, dataDir)
 	if err == nil {
 		t.Fatal("startup should fail when the data directory is not writable")
 	}
 	want := "data directory " + dataDir + " is not writable"
 	if !strings.Contains(err.Error(), want) {
 		t.Errorf("startup error %q does not contain %q", err, want)
 	}
 }
 // TestStartupFailsWhenExistingDataDirNotWritable verifies that startup
 // stops when the data directory exists but the temp file that saving uses
 // cannot be written in it. A directory sitting at the temp file's path
 // makes that write fail, which also holds as root.
 func TestStartupFailsWhenExistingDataDirNotWritable(t *testing.T) {
 	t.Parallel()
 	dataDir := t.TempDir()
 	err := os.Mkdir(filepath.Join(dataDir, "state.json.tmp"), 0o700)
 	if err != nil {
 		t.Fatalf("creating directory: %v", err)
 	}
 	err = startState(t, dataDir)
 	if err == nil {
 		t.Fatal("startup should fail when the data directory is not writable")
 	}
 	want := "data directory " + dataDir + " is not writable"
 	if !strings.Contains(err.Error(), want) {
 		t.Errorf("startup error %q does not contain %q", err, want)
 	}
 }
 // TestStartupCreatesDataDir verifies that startup creates a missing
 // data directory and leaves nothing behind in it.
 func TestStartupCreatesDataDir(t *testing.T) {
 	t.Parallel()
 	dataDir := filepath.Join(t.TempDir(), "data")
 	err := startState(t, dataDir)
 	if err != nil {
 		t.Fatalf("startup error: %v", err)
 	}
 	entries, err := os.ReadDir(dataDir)
 	if err != nil {
 		t.Fatalf("reading data directory: %v", err)
 	}
 	if len(entries) != 0 {
 		t.Errorf("startup left %d entries in the data directory", len(entries))
 	}
 }
 // TestPortStateUnmarshalJSON_NewFormat verifies deserialization of the
 // current multi-hostname format.
 func TestPortStateUnmarshalJSON_NewFormat(t *testing.T) {
@@ -1,25 +0,0 @@
 package watcher
 import (
 	"context"
 	"sneak.berlin/go/dnswatcher/internal/state"
 )
 // NewlyDisagreeingPairs exports newlyDisagreeingPairs for testing.
 func NewlyDisagreeingPairs(
 	prev *state.HostnameState,
 	current map[string]map[string][]string,
 ) [][2]string {
 	return newlyDisagreeingPairs(prev, current)
 }
 // DetectHostnameChanges exports detectHostnameChanges for testing.
 func (w *Watcher) DetectHostnameChanges(
 	ctx context.Context,
 	hostname string,
 	prev *state.HostnameState,
 	current map[string]map[string][]string,
 ) {
 	w.detectHostnameChanges(ctx, hostname, prev, current)
 }
@@ -1,182 +0,0 @@
 package watcher_test
 import (
 	"slices"
 	"testing"
 	"sneak.berlin/go/dnswatcher/internal/state"
 	"sneak.berlin/go/dnswatcher/internal/watcher"
 )
 const (
 	host = "www.example.net"
 	nsA  = "a.ns.example.net."
 	nsB  = "b.ns.example.net."
 	nsC  = "c.ns.example.net."
 	ip1  = "192.0.2.1"
 	ip2  = "192.0.2.2"
 	ip3  = "192.0.2.3"
 )
 // hostnameState builds the state a check with these records leaves behind.
 func hostnameState(
 	records map[string]map[string][]string,
 ) *state.HostnameState {
 	hs := &state.HostnameState{
 		RecordsByNameserver: make(map[string]*state.NameserverRecordState),
 	}
 	for ns, recs := range records {
 		hs.RecordsByNameserver[ns] = &state.NameserverRecordState{
 			Records: recs,
 			Status:  "ok",
 		}
 	}
 	return hs
 }
 func TestNewlyDisagreeingPairs(t *testing.T) {
 	t.Parallel()
 	onlyA := map[string]map[string][]string{nsA: {"A": {ip1}}}
 	agree := map[string]map[string][]string{nsA: {"A": {ip1}}, nsB: {"A": {ip1}}}
 	disagree := map[string]map[string][]string{nsA: {"A": {ip1}}, nsB: {"A": {ip2}}}
 	alert := [][2]string{{nsA, nsB}}
 	// b already disagrees with a and c; then c changes, so a and c,
 	// which agreed, now differ.
 	bDiffers := map[string]map[string][]string{
 		nsA: {"A": {ip1}}, nsB: {"A": {ip2}}, nsC: {"A": {ip1}},
 	}
 	cChanges := map[string]map[string][]string{
 		nsA: {"A": {ip1}}, nsB: {"A": {ip2}}, nsC: {"A": {ip3}},
 	}
 	// Each case starts from the state loaded at startup and runs the
 	// checks in order; want[i] is what check i alerts for.
 	tests := []struct {
 		name   string
 		loaded map[string]map[string][]string
 		checks []map[string]map[string][]string
 		want   [][][2]string
 	}{
 		{
 			name:   "disagreement persisting across checks alerts once",
 			loaded: agree,
 			checks: []map[string]map[string][]string{disagree, disagree, disagree},
 			want:   [][][2]string{alert, nil, nil},
 		},
 		{
 			name:   "disagreement starting on a later check alerts on it",
 			loaded: agree,
 			checks: []map[string]map[string][]string{agree, agree, disagree},
 			want:   [][][2]string{nil, nil, alert},
 		},
 		{
 			name:   "disagreement in the loaded state does not alert",
 			loaded: disagree,
 			checks: []map[string]map[string][]string{disagree, disagree},
 			want:   [][][2]string{nil, nil},
 		},
 		{
 			name:   "nameserver new on the first check and disagreeing alerts once",
 			loaded: onlyA,
 			checks: []map[string]map[string][]string{disagree, disagree},
 			want:   [][][2]string{alert, nil},
 		},
 		{
 			name:   "disagreement after agreeing again alerts again",
 			loaded: agree,
 			checks: []map[string]map[string][]string{disagree, agree, disagree},
 			want:   [][][2]string{alert, nil, alert},
 		},
 		{
 			name:   "new disagreement while another nameserver differs alerts",
 			loaded: bDiffers,
 			checks: []map[string]map[string][]string{cChanges, cChanges},
 			want:   [][][2]string{{{nsA, nsC}}, nil},
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 			prev := hostnameState(tt.loaded)
 			for i, current := range tt.checks {
 				got := watcher.NewlyDisagreeingPairs(prev, current)
 				if !slices.Equal(got, tt.want[i]) {
 					t.Errorf(
 						"check %d: alerted for %v, want %v",
 						i, got, tt.want[i],
 					)
 				}
 				prev = hostnameState(current)
 			}
 		})
 	}
 }
 func TestInconsistencyAlert(t *testing.T) {
 	t.Parallel()
 	onlyA := map[string]map[string][]string{nsA: {"A": {ip1}}}
 	agree := map[string]map[string][]string{nsA: {"A": {ip1}}, nsB: {"A": {ip1}}}
 	disagree := map[string]map[string][]string{nsA: {"A": {ip1}}, nsB: {"A": {ip2}}}
 	// Each case starts from the state loaded at startup and then sees
 	// the nameservers disagree on three checks in a row.
 	tests := []struct {
 		name   string
 		loaded map[string]map[string][]string
 		want   int
 	}{
 		{
 			name:   "disagreement lasting several checks alerts once",
 			loaded: agree,
 			want:   1,
 		},
 		{
 			name:   "disagreement in the loaded state does not alert",
 			loaded: disagree,
 			want:   0,
 		},
 		{
 			name:   "nameserver new on the first check and disagreeing alerts once",
 			loaded: onlyA,
 			want:   1,
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 			// The hostname change detection uses only the notifier.
 			notifier := &mockNotifier{}
 			w := watcher.NewForTest(nil, nil, nil, nil, nil, notifier)
 			prev := hostnameState(tt.loaded)
 			for range 3 {
 				w.DetectHostnameChanges(t.Context(), host, prev, disagree)
 				prev = hostnameState(disagree)
 			}
 			got := 0
 			for _, n := range notifier.getNotifications() {
 				if n.Title == "Inconsistency: "+host {
 					got++
 				}
 			}
 			if got != tt.want {
 				t.Errorf("sent %d inconsistency alerts, want %d", got, tt.want)
 			}
 		})
 	}
 }
@@ -366,7 +366,7 @@ func (w *Watcher) detectHostnameChanges(
 ) {
 	w.detectRecordChanges(ctx, hostname, prev, current)
 	w.detectNSDisappearances(ctx, hostname, prev, current)
-	w.detectInconsistencies(ctx, hostname, prev, current)
+	w.detectInconsistencies(ctx, hostname, current)
 }
 func (w *Watcher) detectRecordChanges(
@@ -448,11 +448,22 @@ func (w *Watcher) detectNSDisappearances(
 func (w *Watcher) detectInconsistencies(
 	ctx context.Context,
 	hostname string,
 	prev *state.HostnameState,
 	current map[string]map[string][]string,
 ) {
-	for _, pair := range newlyDisagreeingPairs(prev, current) {
+	nameservers := make([]string, 0, len(current))
-		ns1, ns2 := pair[0], pair[1]
+	for ns := range current {
 		nameservers = append(nameservers, ns)
 	}
 	sort.Strings(nameservers)
 	for i := range len(nameservers) - 1 {
 		ns1 := nameservers[i]
 		ns2 := nameservers[i+1]
 		if recordsEqual(current[ns1], current[ns2]) {
 			continue
 		}
 		msg := fmt.Sprintf(
 			"Hostname: %s\n%s: %v\n%s: %v",
@@ -470,43 +481,6 @@ func (w *Watcher) detectInconsistencies(
 	}
 }
 // newlyDisagreeingPairs returns every pair of nameservers whose records
 // differ in current, in sorted order of name, except pairs where both
 // nameservers were in prev and already differed there. A nameserver
 // missing from prev is paired with every nameserver it differs from.
 func newlyDisagreeingPairs(
 	prev *state.HostnameState,
 	current map[string]map[string][]string,
 ) [][2]string {
 	nameservers := make([]string, 0, len(current))
 	for ns := range current {
 		nameservers = append(nameservers, ns)
 	}
 	sort.Strings(nameservers)
 	var pairs [][2]string
 	for i, ns1 := range nameservers {
 		for _, ns2 := range nameservers[i+1:] {
 			if recordsEqual(current[ns1], current[ns2]) {
 				continue
 			}
 			prev1, ok1 := prev.RecordsByNameserver[ns1]
 			prev2, ok2 := prev.RecordsByNameserver[ns2]
 			if ok1 && ok2 && !recordsEqual(prev1.Records, prev2.Records) {
 				continue
 			}
 			pairs = append(pairs, [2]string{ns1, ns2})
 		}
 	}
 	return pairs
 }
 func (w *Watcher) checkAllPorts(ctx context.Context) {
 	// Phase 1: Build current IP:port → hostname associations
 	// from fresh DNS data.
@@ -2,77 +2,151 @@ package watcher_test
 import (
 	"context"
 	"errors"
 	"fmt"
 	"log/slog"
 	"slices"
 	"sync"
 	"testing"
 	"time"
 	"sneak.berlin/go/dnswatcher/internal/config"
 	"sneak.berlin/go/dnswatcher/internal/livednstest"
 	"sneak.berlin/go/dnswatcher/internal/portcheck"
 	"sneak.berlin/go/dnswatcher/internal/resolver"
 	"sneak.berlin/go/dnswatcher/internal/state"
 	"sneak.berlin/go/dnswatcher/internal/tlscheck"
 	"sneak.berlin/go/dnswatcher/internal/watcher"
 )
-// The watcher looks these names up in live DNS with the real resolver,
+// errNotFound is returned when mock data is missing.
-// so tests assert on what the watcher does with the answers, never on
+var errNotFound = errors.New("not found")
-// the records these zones publish. testHost's nameservers and addresses
+
-// stay the same from one check to the next, which the tests that check
+// Fixture values shared across tests.
 // it twice rely on.
 const (
-	testDomain = "google.com"
+	testDomain = "example.com"
-	testHost   = "cloudflare.com"
+	testHost   = "www.example.com"
 	testNS1    = "ns1.example.com."
 	testNS2    = "ns2.example.com."
 	testIPv4   = "93.184.216.34"
 	testIP     = "1.2.3.4"
 	testIssuer = "DigiCert"
 )
-// Saved-state values that live DNS never returns: nameserver names
+// --- Mock implementations ---
 // under .invalid and a documentation address.
 const (
 	oldNS1 = "ns1.example.invalid."
 	oldNS2 = "ns2.example.invalid."
 	oldIP  = "192.0.2.1"
 )
-// --- Stand-ins for the port checker, TLS checker and notifier ---
+type mockResolver struct {
-//
+	mu             sync.Mutex
-// DNS has none: the watchers built here use the real resolver (see
+	nsRecords      map[string][]string
-// TESTING.md).
+	allRecords     map[string]map[string]map[string][]string
 	ipAddresses    map[string][]string
 	lookupNSErr    error
 	allRecordsErr  error
 	resolveIPErr   error
 	lookupNSCalls  int
 	allRecordCalls int
 }
 func (m *mockResolver) LookupNS(
 	_ context.Context,
 	domain string,
 ) ([]string, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.lookupNSCalls++
 	if m.lookupNSErr != nil {
 		return nil, m.lookupNSErr
 	}
 	ns, ok := m.nsRecords[domain]
 	if !ok {
 		return nil, fmt.Errorf(
 			"%w: NS for %s", errNotFound, domain,
 		)
 	}
 	return ns, nil
 }
 func (m *mockResolver) LookupAllRecords(
 	_ context.Context,
 	hostname string,
 ) (map[string]map[string][]string, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.allRecordCalls++
 	if m.allRecordsErr != nil {
 		return nil, m.allRecordsErr
 	}
 	recs, ok := m.allRecords[hostname]
 	if !ok {
 		return nil, fmt.Errorf(
 			"%w: records for %s", errNotFound, hostname,
 		)
 	}
 	return recs, nil
 }
 func (m *mockResolver) ResolveIPAddresses(
 	_ context.Context,
 	hostname string,
 ) ([]string, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	if m.resolveIPErr != nil {
 		return nil, m.resolveIPErr
 	}
 	ips, ok := m.ipAddresses[hostname]
 	if !ok {
 		return nil, fmt.Errorf(
 			"%w: IPs for %s", errNotFound, hostname,
 		)
 	}
 	return ips, nil
 }
 // mockPortChecker reports every port open until closed is set.
 type mockPortChecker struct {
-	mu     sync.Mutex
+	mu      sync.Mutex
-	closed bool
+	results map[string]bool
-	calls  int
+	err     error
 	calls   int
 }
 func (m *mockPortChecker) CheckPort(
 	_ context.Context,
-	_ string,
+	address string,
-	_ int,
+	port int,
 ) (*portcheck.PortResult, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.calls++
-	return &portcheck.PortResult{Open: !m.closed}, nil
+	if m.err != nil {
 		return nil, m.err
 	}
 	key := fmt.Sprintf("%s:%d", address, port)
 	open := m.results[key]
 	return &portcheck.PortResult{Open: open}, nil
 }
 // mockTLSChecker returns a certificate for the requested hostname that
 // expires at notAfter.
 type mockTLSChecker struct {
-	mu       sync.Mutex
+	mu    sync.Mutex
-	notAfter time.Time
+	certs map[string]*tlscheck.CertificateInfo
-	calls    int
+	err   error
 	calls int
 }
 func (m *mockTLSChecker) CheckCertificate(
 	_ context.Context,
-	_ string,
+	ip string,
 	hostname string,
 ) (*tlscheck.CertificateInfo, error) {
 	m.mu.Lock()
@@ -80,12 +154,20 @@ func (m *mockTLSChecker) CheckCertificate(
 	m.calls++
-	return &tlscheck.CertificateInfo{
+	if m.err != nil {
-		CommonName:              hostname,
+		return nil, m.err
-		Issuer:                  testIssuer,
+	}
-		NotAfter:                m.notAfter,
+
-		SubjectAlternativeNames: []string{hostname},
+	key := fmt.Sprintf("%s:%s", ip, hostname)
-	}, nil
+	cert, ok := m.certs[key]
 	if !ok {
 		return nil, fmt.Errorf(
 			"%w: cert for %s", errNotFound, key,
 		)
 	}
 	return cert, nil
 }
 type notification struct {
@@ -123,9 +205,10 @@ func (m *mockNotifier) getNotifications() []notification {
 	return result
 }
-// --- Helpers to build a Watcher and run its checks against live DNS ---
+// --- Helper to build a Watcher for testing ---
 type testDeps struct {
 	resolver    *mockResolver
 	portChecker *mockPortChecker
 	tlsChecker  *mockTLSChecker
 	notifier    *mockNotifier
@@ -140,9 +223,16 @@ func newTestWatcher(
 	t.Helper()
 	deps := &testDeps{
-		portChecker: &mockPortChecker{},
+		resolver: &mockResolver{
 			nsRecords:   make(map[string][]string),
 			allRecords:  make(map[string]map[string]map[string][]string),
 			ipAddresses: make(map[string][]string),
 		},
 		portChecker: &mockPortChecker{
 			results: make(map[string]bool),
 		},
 		tlsChecker: &mockTLSChecker{
-			notAfter: time.Now().Add(90 * 24 * time.Hour),
+			certs: make(map[string]*tlscheck.CertificateInfo),
 		},
 		notifier: &mockNotifier{},
 		config:   cfg,
@@ -153,7 +243,7 @@ func newTestWatcher(
 	w := watcher.NewForTest(
 		deps.config,
 		deps.state,
-		resolver.NewFromLogger(slog.Default()),
+		deps.resolver,
 		deps.portChecker,
 		deps.tlsChecker,
 		deps.notifier,
@@ -173,122 +263,6 @@ func defaultTestConfig(t *testing.T) *config.Config {
 	}
 }
 // checkOnce runs the watcher's checks once and returns an error when a
 // configured name has no hostname state saved by this check, or that
 // state holds no address. Either live DNS gave no answer for the name,
 // or the watcher saved no fresh result for it.
 func checkOnce(
 	ctx context.Context,
 	w *watcher.Watcher,
 	deps *testDeps,
 ) error {
 	started := time.Now()
 	w.RunOnce(ctx)
 	names := slices.Concat(deps.config.Domains, deps.config.Hostnames)
 	for _, name := range names {
 		hs, ok := deps.state.GetHostnameState(name)
 		if !ok || hs.LastChecked.Before(started) ||
 			len(addresses(hs)) == 0 {
 			return fmt.Errorf(
 				"%s: %w, or the watcher saved no fresh "+
 					"result for it",
 				name, livednstest.ErrNoAnswer,
 			)
 		}
 	}
 	return nil
 }
 // runChecks builds a watcher, lets prepare set up the saved state and
 // stand-ins it starts from, and runs its checks once against live DNS.
 // If change is not nil, change then alters the saved state or stand-ins
 // and the checks run a second time. When either check finds no fresh
 // address for a name (see checkOnce), the watcher is thrown away and
 // all of this runs again on a new one, so a failed attempt leaves
 // nothing behind in the saved state, the stand-ins or the notifications.
 func runChecks(
 	t *testing.T,
 	cfg *config.Config,
 	prepare, change func(deps *testDeps),
 ) *testDeps {
 	t.Helper()
 	var deps *testDeps
 	livednstest.Retry(t, "watcher checks", func(ctx context.Context) error {
 		var w *watcher.Watcher
 		w, deps = newTestWatcher(t, cfg)
 		if prepare != nil {
 			prepare(deps)
 		}
 		err := checkOnce(ctx, w, deps)
 		if err != nil || change == nil {
 			return err
 		}
 		change(deps)
 		return checkOnce(ctx, w, deps)
 	})
 	return deps
 }
 // addresses returns the A and AAAA values saved for a hostname.
 func addresses(hs *state.HostnameState) []string {
 	var ips []string
 	for _, nsState := range hs.RecordsByNameserver {
 		ips = append(ips, nsState.Records["A"]...)
 		ips = append(ips, nsState.Records["AAAA"]...)
 	}
 	return ips
 }
 // assertNotified checks that a notification with this title and
 // priority was sent.
 func assertNotified(
 	t *testing.T,
 	deps *testDeps,
 	title, priority string,
 ) {
 	t.Helper()
 	notifications := deps.notifier.getNotifications()
 	for _, n := range notifications {
 		if n.Title == title && n.Priority == priority {
 			return
 		}
 	}
 	t.Errorf(
 		"expected %s notification %q, got: %v",
 		priority, title, notifications,
 	)
 }
 // countNotifications counts the notifications sent with this title.
 func countNotifications(deps *testDeps, title string) int {
 	count := 0
 	for _, n := range deps.notifier.getNotifications() {
 		if n.Title == title {
 			count++
 		}
 	}
 	return count
 }
 func TestFirstRunBaseline(t *testing.T) {
 	t.Parallel()
@@ -296,12 +270,51 @@ func TestFirstRunBaseline(t *testing.T) {
 	cfg.Domains = []string{testDomain}
 	cfg.Hostnames = []string{testHost}
-	deps := runChecks(t, cfg, nil, nil)
+	w, deps := newTestWatcher(t, cfg)
 	setupBaselineMocks(deps)
 	w.RunOnce(t.Context())
 	assertNoNotifications(t, deps)
 	assertStatePopulated(t, deps)
 }
 func setupBaselineMocks(deps *testDeps) {
 	deps.resolver.nsRecords[testDomain] = []string{
 		testNS1,
 		testNS2,
 	}
 	deps.resolver.allRecords[testDomain] = map[string]map[string][]string{
 		testNS1: {"A": {testIPv4}},
 		testNS2: {"A": {testIPv4}},
 	}
 	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
 		testNS1: {"A": {testIPv4}},
 		testNS2: {"A": {testIPv4}},
 	}
 	deps.resolver.ipAddresses[testHost] = []string{
 		testIPv4,
 	}
 	deps.portChecker.results["93.184.216.34:80"] = true
 	deps.portChecker.results["93.184.216.34:443"] = true
 	deps.tlsChecker.certs["93.184.216.34:www.example.com"] = &tlscheck.CertificateInfo{
 		CommonName: testHost,
 		Issuer:     testIssuer,
 		NotAfter:   time.Now().Add(90 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{
 			testHost,
 		},
 	}
 	deps.tlsChecker.certs["93.184.216.34:example.com"] = &tlscheck.CertificateInfo{
 		CommonName: testDomain,
 		Issuer:     testIssuer,
 		NotAfter:   time.Now().Add(90 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{
 			testDomain,
 		},
 	}
 }
 func assertNoNotifications(
 	t *testing.T,
 	deps *testDeps,
@@ -348,7 +361,26 @@ func TestDomainPortAndTLSChecks(t *testing.T) {
 	cfg := defaultTestConfig(t)
 	cfg.Domains = []string{testDomain}
-	deps := runChecks(t, cfg, nil, nil)
+	w, deps := newTestWatcher(t, cfg)
 	deps.resolver.nsRecords[testDomain] = []string{
 		testNS1,
 	}
 	deps.resolver.allRecords[testDomain] = map[string]map[string][]string{
 		testNS1: {"A": {testIPv4}},
 	}
 	deps.portChecker.results["93.184.216.34:80"] = true
 	deps.portChecker.results["93.184.216.34:443"] = true
 	deps.tlsChecker.certs["93.184.216.34:example.com"] = &tlscheck.CertificateInfo{
 		CommonName: testDomain,
 		Issuer:     testIssuer,
 		NotAfter:   time.Now().Add(90 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{
 			testDomain,
 		},
 	}
 	w.RunOnce(t.Context())
 	snap := deps.state.GetSnapshot()
@@ -387,18 +419,50 @@ func TestNSChangeDetection(t *testing.T) {
 	cfg := defaultTestConfig(t)
 	cfg.Domains = []string{testDomain}
-	// The saved state lists nameservers that live DNS does not.
+	w, deps := newTestWatcher(t, cfg)
 	deps := runChecks(t, cfg, func(deps *testDeps) {
 		deps.state.SetDomainState(testDomain, &state.DomainState{
 			Nameservers: []string{oldNS1, oldNS2},
 		})
 	}, nil)
-	assertNotified(t, deps, "NS Change: "+testDomain, "warning")
+	deps.resolver.nsRecords[testDomain] = []string{
 		testNS1,
 		testNS2,
 	}
 	deps.resolver.allRecords[testDomain] = map[string]map[string][]string{
 		testNS1: {"A": {testIP}},
 		testNS2: {"A": {testIP}},
 	}
 	deps.portChecker.results["1.2.3.4:80"] = false
 	deps.portChecker.results["1.2.3.4:443"] = false
-	ds, _ := deps.state.GetDomainState(testDomain)
+	ctx := t.Context()
-	if slices.Contains(ds.Nameservers, oldNS1) {
+	w.RunOnce(ctx)
-		t.Errorf("saved nameservers not updated: %v", ds.Nameservers)
+
 	deps.resolver.mu.Lock()
 	deps.resolver.nsRecords[testDomain] = []string{
 		testNS1,
 		"ns3.example.com.",
 	}
 	deps.resolver.allRecords[testDomain] = map[string]map[string][]string{
 		testNS1:            {"A": {testIP}},
 		"ns3.example.com.": {"A": {testIP}},
 	}
 	deps.resolver.mu.Unlock()
 	w.RunOnce(ctx)
 	notifications := deps.notifier.getNotifications()
 	if len(notifications) == 0 {
 		t.Error("expected notification for NS change")
 	}
 	found := false
 	for _, n := range notifications {
 		if n.Priority == "warning" {
 			found = true
 		}
 	}
 	if !found {
 		t.Error("expected warning-priority NS change notification")
 	}
 }
@@ -408,18 +472,40 @@ func TestRecordChangeDetection(t *testing.T) {
 	cfg := defaultTestConfig(t)
 	cfg.Hostnames = []string{testHost}
-	// Between the checks, save for every nameserver an address live DNS
+	w, deps := newTestWatcher(t, cfg)
 	// never returns.
 	deps := runChecks(t, cfg, nil, func(deps *testDeps) {
 		hs, _ := deps.state.GetHostnameState(testHost)
 		for _, nsState := range hs.RecordsByNameserver {
 			nsState.Records = map[string][]string{"A": {oldIP}}
 		}
-		deps.state.SetHostnameState(testHost, hs)
+	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
-	})
+		testNS1: {"A": {testIPv4}},
 	}
 	deps.resolver.ipAddresses[testHost] = []string{
 		testIPv4,
 	}
 	deps.portChecker.results["93.184.216.34:80"] = false
 	deps.portChecker.results["93.184.216.34:443"] = false
-	assertNotified(t, deps, "Record Change: "+testHost, "warning")
+	ctx := t.Context()
 	w.RunOnce(ctx)
 	deps.resolver.mu.Lock()
 	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
 		testNS1: {"A": {"93.184.216.35"}},
 	}
 	deps.resolver.ipAddresses[testHost] = []string{
 		"93.184.216.35",
 	}
 	deps.resolver.mu.Unlock()
 	deps.portChecker.mu.Lock()
 	deps.portChecker.results["93.184.216.35:80"] = false
 	deps.portChecker.results["93.184.216.35:443"] = false
 	deps.portChecker.mu.Unlock()
 	w.RunOnce(ctx)
 	notifications := deps.notifier.getNotifications()
 	if len(notifications) == 0 {
 		t.Error("expected notification for record change")
 	}
 }
 func TestPortStateChange(t *testing.T) {
@@ -428,23 +514,38 @@ func TestPortStateChange(t *testing.T) {
 	cfg := defaultTestConfig(t)
 	cfg.Hostnames = []string{testHost}
-	// Between the checks, every port closes.
+	w, deps := newTestWatcher(t, cfg)
 	deps := runChecks(t, cfg, nil, func(deps *testDeps) {
 		deps.portChecker.mu.Lock()
 		deps.portChecker.closed = true
 		deps.portChecker.mu.Unlock()
 	})
-	hs, _ := deps.state.GetHostnameState(testHost)
+	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
-	assertNotified(
+		testNS1: {"A": {testIP}},
-		t, deps, "Port Change: "+addresses(hs)[0]+":443", "warning",
+	}
-	)
+	deps.resolver.ipAddresses[testHost] = []string{
-}
+		testIP,
 	}
 	deps.portChecker.results["1.2.3.4:80"] = true
 	deps.portChecker.results["1.2.3.4:443"] = true
 	deps.tlsChecker.certs["1.2.3.4:www.example.com"] = &tlscheck.CertificateInfo{
 		CommonName: testHost,
 		Issuer:     testIssuer,
 		NotAfter:   time.Now().Add(90 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{
 			testHost,
 		},
 	}
-// expiresInThreeDays makes the TLS checker return certificates that
+	ctx := t.Context()
-// expire within the seven-day warning period.
+	w.RunOnce(ctx)
-func expiresInThreeDays(deps *testDeps) {
+
-	deps.tlsChecker.notAfter = time.Now().Add(3 * 24 * time.Hour)
+	deps.portChecker.mu.Lock()
 	deps.portChecker.results["1.2.3.4:443"] = false
 	deps.portChecker.mu.Unlock()
 	w.RunOnce(ctx)
 	notifications := deps.notifier.getNotifications()
 	if len(notifications) == 0 {
 		t.Error("expected notification for port state change")
 	}
 }
 func TestTLSExpiryWarning(t *testing.T) {
@@ -453,9 +554,49 @@ func TestTLSExpiryWarning(t *testing.T) {
 	cfg := defaultTestConfig(t)
 	cfg.Hostnames = []string{testHost}
-	deps := runChecks(t, cfg, expiresInThreeDays, nil)
+	w, deps := newTestWatcher(t, cfg)
-	assertNotified(t, deps, "TLS Expiry Warning: "+testHost, "warning")
+	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
 		testNS1: {"A": {testIP}},
 	}
 	deps.resolver.ipAddresses[testHost] = []string{
 		testIP,
 	}
 	deps.portChecker.results["1.2.3.4:80"] = true
 	deps.portChecker.results["1.2.3.4:443"] = true
 	deps.tlsChecker.certs["1.2.3.4:www.example.com"] = &tlscheck.CertificateInfo{
 		CommonName: testHost,
 		Issuer:     testIssuer,
 		NotAfter:   time.Now().Add(3 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{
 			testHost,
 		},
 	}
 	ctx := t.Context()
 	// First run = baseline
 	w.RunOnce(ctx)
 	// Second run should warn about expiry
 	w.RunOnce(ctx)
 	notifications := deps.notifier.getNotifications()
 	found := false
 	for _, n := range notifications {
 		if n.Priority == "warning" {
 			found = true
 		}
 	}
 	if !found {
 		t.Errorf(
 			"expected expiry warning, got: %v",
 			notifications,
 		)
 	}
 }
 func TestTLSExpiryWarningDedup(t *testing.T) {
@@ -465,25 +606,50 @@ func TestTLSExpiryWarningDedup(t *testing.T) {
 	cfg.Hostnames = []string{testHost}
 	cfg.TLSInterval = 24 * time.Hour
-	title := "TLS Expiry Warning: " + testHost
+	w, deps := newTestWatcher(t, cfg)
-	// The second check comes within the TLS interval of the first,
+	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
-	// so it must not warn again.
+		testNS1: {"A": {testIP}},
-	var warnings int
+	}
-
+	deps.resolver.ipAddresses[testHost] = []string{
-	deps := runChecks(t, cfg, expiresInThreeDays, func(deps *testDeps) {
+		testIP,
-		warnings = countNotifications(deps, title)
+	}
-	})
+	deps.portChecker.results["1.2.3.4:80"] = true
-
+	deps.portChecker.results["1.2.3.4:443"] = true
-	if warnings == 0 {
+	deps.tlsChecker.certs["1.2.3.4:www.example.com"] = &tlscheck.CertificateInfo{
-		t.Fatal("expected expiry warnings from the first check")
+		CommonName: testHost,
 		Issuer:     testIssuer,
 		NotAfter:   time.Now().Add(3 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{
 			testHost,
 		},
 	}
-	got := countNotifications(deps, title)
+	ctx := t.Context()
-	if got != warnings {
+
 	// First run = baseline, no notifications
 	w.RunOnce(ctx)
 	// Second run should fire one expiry warning
 	w.RunOnce(ctx)
 	// Third run should NOT fire another warning (dedup)
 	w.RunOnce(ctx)
 	notifications := deps.notifier.getNotifications()
 	expiryCount := 0
 	for _, n := range notifications {
 		if n.Title == "TLS Expiry Warning: www.example.com" {
 			expiryCount++
 		}
 	}
 	if expiryCount != 1 {
 		t.Errorf(
-			"expected %d expiry warnings (dedup), got %d",
+			"expected exactly 1 expiry warning (dedup), got %d",
-			warnings, got,
+			expiryCount,
 		)
 	}
 }
@@ -491,12 +657,21 @@ func TestTLSExpiryWarningDedup(t *testing.T) {
 func TestGracefulShutdown(t *testing.T) {
 	t.Parallel()
 	// No domains or hostnames: stopping does not involve DNS.
 	cfg := defaultTestConfig(t)
 	cfg.Domains = []string{testDomain}
 	cfg.DNSInterval = 100 * time.Millisecond
 	cfg.TLSInterval = 100 * time.Millisecond
-	w, _ := newTestWatcher(t, cfg)
+	w, deps := newTestWatcher(t, cfg)
 	deps.resolver.nsRecords[testDomain] = []string{
 		testNS1,
 	}
 	deps.resolver.allRecords[testDomain] = map[string]map[string][]string{
 		testNS1: {"A": {testIP}},
 	}
 	deps.portChecker.results["1.2.3.4:80"] = false
 	deps.portChecker.results["1.2.3.4:443"] = false
 	ctx, cancel := context.WithCancel(t.Context())
@@ -518,52 +693,90 @@ func TestGracefulShutdown(t *testing.T) {
 	}
 }
 func setupHostnameIP(
 	deps *testDeps,
 	hostname, ip string,
 ) {
 	deps.resolver.allRecords[hostname] = map[string]map[string][]string{
 		testNS1: {"A": {ip}},
 	}
 	deps.portChecker.results[ip+":80"] = true
 	deps.portChecker.results[ip+":443"] = true
 	deps.tlsChecker.certs[ip+":"+hostname] = &tlscheck.CertificateInfo{
 		CommonName:              hostname,
 		Issuer:                  testIssuer,
 		NotAfter:                time.Now().Add(90 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{hostname},
 	}
 }
 func updateHostnameIP(deps *testDeps, hostname, ip string) {
 	deps.resolver.mu.Lock()
 	deps.resolver.allRecords[hostname] = map[string]map[string][]string{
 		testNS1: {"A": {ip}},
 	}
 	deps.resolver.mu.Unlock()
 	deps.portChecker.mu.Lock()
 	deps.portChecker.results[ip+":80"] = true
 	deps.portChecker.results[ip+":443"] = true
 	deps.portChecker.mu.Unlock()
 	deps.tlsChecker.mu.Lock()
 	deps.tlsChecker.certs[ip+":"+hostname] = &tlscheck.CertificateInfo{
 		CommonName:              hostname,
 		Issuer:                  testIssuer,
 		NotAfter:                time.Now().Add(90 * 24 * time.Hour),
 		SubjectAlternativeNames: []string{hostname},
 	}
 	deps.tlsChecker.mu.Unlock()
 }
 func TestDNSRunsBeforePortAndTLSChecks(t *testing.T) {
 	t.Parallel()
 	cfg := defaultTestConfig(t)
 	cfg.Hostnames = []string{testHost}
-	// The saved state says the last check found testHost at oldIP.
+	w, deps := newTestWatcher(t, cfg)
-	deps := runChecks(t, cfg, func(deps *testDeps) {
+
-		deps.state.SetHostnameState(testHost, &state.HostnameState{
+	setupHostnameIP(deps, testHost, "10.0.0.1")
-			RecordsByNameserver: map[string]*state.NameserverRecordState{
+
-				oldNS1: {
+	ctx := t.Context()
-					Records: map[string][]string{"A": {oldIP}},
+	w.RunOnce(ctx)
 					Status:  "ok",
 				},
 			},
 		})
 	}, nil)
 	snap := deps.state.GetSnapshot()
-
+	if _, ok := snap.Ports["10.0.0.1:80"]; !ok {
-	if _, ok := snap.Ports[oldIP+":80"]; ok {
+		t.Fatal("expected port state for 10.0.0.1:80")
 		t.Error("port check used stale DNS: found " + oldIP + ":80")
 	}
-	// Port and TLS checks must use the addresses this check found.
+	// DNS changes to a new IP; port and TLS must pick it up.
-	for _, ip := range addresses(snap.Hostnames[testHost]) {
+	updateHostnameIP(deps, testHost, "10.0.0.2")
 		if _, ok := snap.Ports[ip+":80"]; !ok {
 			t.Error("port check used stale DNS: missing " + ip + ":80")
 		}
-		certKey := ip + ":443:" + testHost
+	w.RunOnce(ctx)
-		if _, ok := snap.Certificates[certKey]; !ok {
+
-			t.Error("TLS check used stale DNS: missing " + certKey)
+	snap = deps.state.GetSnapshot()
-		}
+
 	if _, ok := snap.Ports["10.0.0.2:80"]; !ok {
 		t.Error("port check used stale DNS: missing 10.0.0.2:80")
 	}
 	certKey := "10.0.0.2:443:www.example.com"
 	if _, ok := snap.Certificates[certKey]; !ok {
 		t.Error("TLS check used stale DNS: missing " + certKey)
 	}
 }
 func TestSendTestNotification_Enabled(t *testing.T) {
 	t.Parallel()
 	// No domains or hostnames: the startup notification does not
 	// involve DNS.
 	cfg := defaultTestConfig(t)
 	cfg.Domains = []string{testDomain}
 	cfg.Hostnames = []string{testHost}
 	cfg.SendTestNotification = true
 	w, deps := newTestWatcher(t, cfg)
 	setupBaselineMocks(deps)
 	w.RunOnce(t.Context())
@@ -584,11 +797,14 @@ func TestSendTestNotification_ViaRun(t *testing.T) {
 	t.Parallel()
 	cfg := defaultTestConfig(t)
 	cfg.Domains = []string{testDomain}
 	cfg.Hostnames = []string{testHost}
 	cfg.SendTestNotification = true
 	cfg.DNSInterval = 24 * time.Hour
 	cfg.TLSInterval = 24 * time.Hour
 	w, deps := newTestWatcher(t, cfg)
 	setupBaselineMocks(deps)
 	ctx, cancel := context.WithCancel(t.Context())
@@ -628,11 +844,14 @@ func TestSendTestNotification_Disabled(t *testing.T) {
 	t.Parallel()
 	cfg := defaultTestConfig(t)
 	cfg.Domains = []string{testDomain}
 	cfg.Hostnames = []string{testHost}
 	cfg.SendTestNotification = false
 	cfg.DNSInterval = 24 * time.Hour
 	cfg.TLSInterval = 24 * time.Hour
 	w, deps := newTestWatcher(t, cfg)
 	setupBaselineMocks(deps)
 	ctx, cancel := context.WithCancel(t.Context())
@@ -665,22 +884,32 @@ func TestNSFailureAndRecovery(t *testing.T) {
 	cfg := defaultTestConfig(t)
 	cfg.Hostnames = []string{testHost}
-	// Between the checks, save every nameserver the first check found
+	w, deps := newTestWatcher(t, cfg)
 	// as failed, and add, as answering, one that live DNS does not list.
 	deps := runChecks(t, cfg, nil, func(deps *testDeps) {
 		hs, _ := deps.state.GetHostnameState(testHost)
 		for _, nsState := range hs.RecordsByNameserver {
 			nsState.Status = "error"
 		}
-		hs.RecordsByNameserver[oldNS1] = &state.NameserverRecordState{
+	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
-			Records: map[string][]string{"A": {oldIP}},
+		testNS1: {"A": {testIP}},
-			Status:  "ok",
+		testNS2: {"A": {testIP}},
-		}
+	}
 	deps.resolver.ipAddresses[testHost] = []string{
 		testIP,
 	}
 	deps.portChecker.results["1.2.3.4:80"] = false
 	deps.portChecker.results["1.2.3.4:443"] = false
-		deps.state.SetHostnameState(testHost, hs)
+	ctx := t.Context()
 	})
-	assertNotified(t, deps, "NS Failure: "+testHost, "error")
+	w.RunOnce(ctx)
-	assertNotified(t, deps, "NS Recovery: "+testHost, "success")
+
 	deps.resolver.mu.Lock()
 	deps.resolver.allRecords[testHost] = map[string]map[string][]string{
 		testNS1: {"A": {testIP}},
 	}
 	deps.resolver.mu.Unlock()
 	w.RunOnce(ctx)
 	notifications := deps.notifier.getNotifications()
 	if len(notifications) == 0 {
 		t.Error("expected notification for NS disappearance")
 	}
 }
@@ -1,18 +1,14 @@
 #!/bin/sh
 # script/cibuild: run the CI build. The Dockerfile's lint stage runs
 # make fmt-check and golangci-lint; its builder stage runs make test
-# and make build.
+# and make build. A successful build implies all of those passed.
 #
 # --no-cache-filter=lint,builder runs both stages on every invocation;
 # otherwise an unchanged tree is served from the layer cache and passes
 # without linting or querying live DNS.
 set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    docker build --no-cache-filter=lint,builder .
+    docker build .
 }
 main "$@"
@@ -1,10 +1,6 @@
 #!/bin/sh
 # script/docker: build the Docker image tagged with the project name.
-# The tag comes from script/projectname.
+# Identical in all repos; the tag comes from script/projectname.
 #
 # --no-cache-filter=lint,builder runs the lint stage and the builder
 # stage (make test) on every invocation; otherwise an unchanged tree is
 # served from the layer cache without linting or querying live DNS.
 set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -12,7 +8,7 @@ ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    docker build --no-cache-filter=lint,builder -t "$("$SCRIPT_DIR/projectname")" .
+    docker build -t "$("$SCRIPT_DIR/projectname")" .
 }
 main "$@"