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dnswatcher/TESTING.md
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sneak 180e81351a
check / check (push) Failing after 2m14s
fmt: format and check Markdown with prettier in a container (closes #119)
make fmt and make fmt-check now cover every Markdown file with prettier
(4-space tabs, proseWrap always), as template-app-go does: prettier is
pinned by package.json and yarn.lock and runs in a docker build on a
digest-pinned node image, never on the host. The check is forced to run
with --no-cache-filter, as script/lint is.

script/fmt-check is split into a Go half and a Markdown half because the
Dockerfile lint stage cannot run docker: that stage now runs the Go half
and script/cibuild runs the Markdown half after the build. *.md leaves
.dockerignore so documents reach the build context.

README.md, TESTING.md and TODO.md are reformatted by make fmt; apart from
the Entrypoints and TODO entries, that diff is mechanical.

Model: opus-5-5
2026-10-01 22:07:50 +00:00

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# Testing Policy
## DNS Resolution Tests
DNS is never mocked in this project, not in tests and not anywhere else; see the
README section "No DNS mocking. Ever." Every test that 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
The resolver performs iterative resolution from root nameservers through 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.
### Constraints
- Tests hit real DNS infrastructure and require network access
- Test duration depends on network conditions; timeout tuning keeps the suite
within the 60-second target
- 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`, no
stand-in for the watcher's `DNSResolver`, no fake DNS server, no 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 replays a
previous run's output without querying anything, so a cached pass is not
evidence that live resolution works
- **Do not modify linter configuration** to suppress findings