Remove DNS mocking from tests; use live DNS everywhere

DNS is never mocked in this repository: tests exercise live DNS,
and robustness comes from handling real-world DNS behavior with
tolerant assertions and sensible timeouts, not from mocks.

watcher: drop mockResolver and wire the real iterative resolver
into the tests, querying stable public names (example.com,
www.example.com). Change detection is exercised by seeding the
state store with a synthetic previous observation that live DNS
cannot match (reserved .invalid nameserver names and RFC 5737
documentation addresses); DNS stays live in every run. The port
checker, TLS checker, and notifier remain test doubles since they
are not DNS, keeping notification and state assertions
deterministic against whatever addresses live DNS returns.

resolver: drop the timeoutClient fake DNSClient and the
NewFromLoggerWithClient mock constructor. The timeout test is
replaced by a live query against an RFC 5737 documentation
address where no nameserver can exist, asserting a classified
non-OK response with no records.

TESTING.md: extend the live-DNS policy to every package and
remove the carve-out that permitted DNS mocks in packages that
consume the resolver.

TODO.md: update stale references to hermetic mocked-DNS work to
reflect the no-mocking policy and the current state of
feature/resolver.

Intentionally dropped coverage: the exact StatusTimeout
classification (previously forced by the fake client) is no
longer asserted, because a genuinely unreachable server may fail
fast instead of timing out depending on the network path; the
live test tolerantly accepts any failure classification.

TESTING.md

@@ -2,8 +2,10 @@
 
 ## DNS Resolution Tests
 
-All resolver tests **MUST** use live queries against real DNS servers.
+All tests that involve DNS resolution — in every package, including
-No mocking of the DNS client layer is permitted.
+consumers of the resolver such as the watcher — **MUST** use live
+queries against real DNS servers. No mocking, faking, or stubbing of
+DNS at any layer is permitted.
 
 ### Rationale
 
@@ -12,6 +14,8 @@ the full delegation chain. Mocked responses cannot faithfully represent
 the variety of real-world DNS behavior (truncation, referrals, glue
 records, DNSSEC, varied response times, EDNS, etc.). Testing against
 real servers ensures the resolver works correctly in production.
+Robustness comes from handling real-world DNS behavior with tolerant
+assertions and sensible timeouts, not from mocks.
 
 ### Constraints
 
@@ -24,11 +28,14 @@ real servers ensures the resolver works correctly in production.
 - Flaky failures from transient network issues are acceptable and
   should be investigated as potential resolver bugs, not papered over
   with mocks or skip flags
+- Watcher change-detection tests seed a synthetic *previous state*
+  and compare it against fresh live lookups; the DNS side is never
+  faked
 
 ### What NOT to do
 
-- **Do not mock `DNSClient`** for resolver tests (the mock constructor
+- **Do not mock `DNSClient`**, the watcher's `DNSResolver` interface,
-  exists for unit-testing other packages that consume the resolver)
+  or any other DNS abstraction — in any package, for any reason
 - **Do not add `-short` flags** to skip slow tests
 - **Do not increase `-timeout`** to hide hanging queries
 - **Do not modify linter configuration** to suppress findings

TODO.md

@@ -14,7 +14,10 @@ pre-1.0. No git tags. Core resolver work in flight on feature/resolver
 (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.
+iterative resolver implementation. DNS mocking is banned in this repo
+(see `TESTING.md`): all tests use live DNS only. The hermetic mocked
+tests previously noted on `feature/resolver` are gone from its current
+tip, which carries a live-DNS suite against `*.dns.sneak.cloud`.
 
 # Next Step
 
@@ -25,13 +28,10 @@ confirm make check still passes.
 
 # Completed Steps
 
-- 2026-08-09: `script/bootstrap` now installs the pinned `golangci-lint`
+- 2026-08-07: DNS mocking removed from the entire test suite; watcher
-  and `goimports` unconditionally instead of only when the binary is
+  tests now drive the real iterative resolver against live DNS and
-  absent from `PATH`, so the commit pins actually take effect on
+  `TESTING.md` bans DNS mocks in every package (`remove-dns-mocking`
-  already-provisioned machines; it also warns when `PATH` resolves
+  branch)
-  either tool to a copy outside the directory `go install` writes to.
-  The `missing` presence check is retained for `git`, `make`, and `go`
-  (#117)
 - 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
@@ -43,7 +43,8 @@ confirm make check still passes.
 - 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)
+  with mocked DNS (origin/feature/resolver, unmerged; superseded — DNS
+  mocking is banned, see `TESTING.md`)
 - 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)
@@ -70,8 +71,9 @@ Branch reconciliation:
 - Sync local checkout with origin: local main is 8 commits behind
   origin/main; local feature/resolver has diverged from
   origin/feature/resolver, which already implements the resolver
-- Merge in-flight branches to main once green: feature/resolver,
+- Merge in-flight branches to main once green: feature/resolver
-  ci/make-check, feature/portcheck-implementation,
+  (confirm its tests remain live-DNS — DNS mocking is banned, see
+  `TESTING.md`), ci/make-check, feature/portcheck-implementation,
   feature/tlscheck-implementation
 
 Resolver (plan from untracked TODO.md; largely implemented on
@@ -155,6 +157,7 @@ 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
+- Resolver tests originally used live DNS against `*.dns.sneak.cloud`
-  (required records documented in the test file header); origin now has
+  (required records documented in the test file header); `main` now
-  mocked hermetic tests, keep them hermetic
+  tests against live public DNS. DNS mocking is banned (see
+  `TESTING.md`); never reintroduce hermetic mocked DNS tests

internal/resolver/dns_client.go

@@ -7,8 +7,8 @@ import (
 	"github.com/miekg/dns"
 )
 
-// DNSClient abstracts DNS wire-protocol exchanges so the resolver
+// DNSClient abstracts DNS wire-protocol exchanges over a single
-// can be tested without hitting real nameservers.
+// transport, letting the resolver switch between UDP and TCP.
 type DNSClient interface {
 	ExchangeContext(
 		ctx context.Context,

internal/resolver/resolver.go

@@ -67,17 +67,4 @@ 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.

internal/resolver/resolver_test.go

@@ -10,7 +10,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -624,58 +623,41 @@ func TestQueryAllNameservers_ContextCanceled(t *testing.T) {
 }
 
 // ----------------------------------------------------------------
-// Timeout tests
+// Unreachable nameserver tests
 // ----------------------------------------------------------------
 
-func TestQueryNameserverIP_Timeout(t *testing.T) {
+func TestQueryNameserverIP_UnreachableServer(t *testing.T) {
 	t.Parallel()
 
-	log := slog.New(slog.NewTextHandler(
+	r := newTestResolver(t)
-		os.Stderr,
-		&slog.HandlerOptions{Level: slog.LevelDebug},
-	))
-
-	r := resolver.NewFromLoggerWithClient(
-		log, &timeoutClient{},
-	)
 
 	ctx, cancel := context.WithTimeout(
 		context.Background(), 10*time.Second,
 	)
 	t.Cleanup(cancel)
 
-	// Query any IP — the client always returns a timeout error.
+	// 192.0.2.1 is an RFC 5737 documentation address: no
+	// nameserver can exist there. Depending on the network
+	// path the queries either time out (silent drop) or fail
+	// fast (ICMP unreachable), so accept any non-OK status;
+	// the resolver must return a classified response with no
+	// records rather than an error or a hang.
 	resp, err := r.QueryNameserverIP(
 		ctx, "unreachable.test.", "192.0.2.1",
 		"example.com",
 	)
 	require.NoError(t, err)
 
-	assert.Equal(t, resolver.StatusTimeout, resp.Status)
+	assert.NotEqual(t, resolver.StatusOK, resp.Status)
-	assert.NotEmpty(t, resp.Error)
-}
 
-// timeoutClient simulates DNS timeout errors for testing.
+	totalRecords := 0
-type timeoutClient struct{}
+	for _, values := range resp.Records {
-
+		totalRecords += len(values)
-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{},
 	}
+
+	assert.Zero(t, totalRecords)
 }
 
-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()
 

script/bootstrap

@@ -1,13 +1,10 @@
 #!/bin/sh
 # script/bootstrap: install all dependencies needed to build and develop
-# this repo. Base tooling (git, make, go) comes from nix, apt, brew, or
+# this repo. Idempotent: every install is guarded by a check so already
-# apk (detected in that order) and is installed only when absent;
+# installed tools are skipped. Base tooling comes from nix, apt, brew,
-# assumes nothing is present. golangci-lint and goimports are always
+# or apk (detected in that order); assumes nothing is present.
-# (re)installed via `go install` at the same pinned commits the
+# golangci-lint and goimports are installed via `go install` at the same
-# Dockerfile uses (never "latest") -- a presence check cannot tell the
+# pinned commits the Dockerfile uses (never "latest").
-# pinned build from an arbitrary one already on PATH, so guarding them
-# would make the pins inert. Idempotent either way: running this twice
-# succeeds both times and leaves the same result.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
@@ -65,31 +62,6 @@ missing() {
     ! command -v "$1" >/dev/null 2>&1
 }
 
-# go_bin_dir: directory `go install` writes binaries to.
-go_bin_dir() {
-    gobin="$(go env GOBIN)"
-    if [ -n "$gobin" ]; then
-        echo "$gobin"
-    else
-        echo "$(go env GOPATH)/bin"
-    fi
-}
-
-# warn_if_shadowed <tool> <dir>: the pinned build was just installed
-# into <dir>. If PATH resolves <tool> anywhere else, that other copy is
-# what `make lint` and `make fmt` will actually run, and it is not the
-# pinned version. Warn loudly rather than failing, since the fix is the
-# user's PATH and not anything this script can do.
-warn_if_shadowed() {
-    resolved="$(command -v "$1" 2>/dev/null || true)"
-    if [ "$resolved" != "$2/$1" ]; then
-        echo "bootstrap: WARNING: installed pinned $1 to $2/$1, but PATH" >&2
-        echo "bootstrap: WARNING: resolves $1 to ${resolved:-(not on PATH)};" >&2
-        echo "bootstrap: WARNING: put $2 first on PATH or lint results will" >&2
-        echo "bootstrap: WARNING: not match CI." >&2
-    fi
-}
-
 main() {
     cd "$ROOT"
 
@@ -97,17 +69,10 @@ main() {
     if missing make; then pkg_install gnumake make make make; fi
     if missing go; then pkg_install go golang go go; fi
 
-    # Lint/format tools, pinned via go install. These are installed
+    # Lint/format tools, pinned via go install (installs into
-    # unconditionally: `command -v` only proves *some* build is on PATH,
+    # "$(go env GOPATH)/bin"; ensure that is on your PATH).
-    # and a wrong golangci-lint either cannot parse our v2-schema
+    if missing golangci-lint; then go install "$GOLANGCI_LINT_REF"; fi
-    # .golangci.yml at all or silently disagrees with CI. Installing at
+    if missing goimports; then go install "$GOIMPORTS_REF"; fi
-    # a fixed commit ref is idempotent and cheap with a warm module
-    # cache, so there is nothing to save by skipping it.
-    GOBIN_DIR="$(go_bin_dir)"
-    go install "$GOLANGCI_LINT_REF"
-    go install "$GOIMPORTS_REF"
-    warn_if_shadowed golangci-lint "$GOBIN_DIR"
-    warn_if_shadowed goimports "$GOBIN_DIR"
 
     go mod download