[external_dns] strengthen tests to lift mutation score

[philjlee]

What does this PR do?

Strengthens the unit tests for the external_dns check to lift its cosmic-ray mutation score from
33.3% to 100.0% (3/3 mutants killed). Tests-only — no source changes,
no changelog.

Each new test carries a one-line comment naming the specific surviving mutant it kills.

Motivation

A mutation-testing sweep across integrations-core found external_dns scoring 33.3%: source
behavior that no unit test detected. The new/extended env-agnostic tests in tests/test_unit.py
instantiate the real check classes (no mocks, no environment gating) and reuse the existing
tests/common.py fixtures and constants.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.

[datadog-datadog-prod-us1]

 

✅ All CI checks and tests passed.

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 90.91% (+1.85%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 4806e52 | Docs | View more details | Give us feedback!}

[mwdd146980]

don't know if you're still working on this, but this lgtm!

[dd-octo-sts]

✅ Dispatcher tests · passed

Dispatcher beta: informational only

Dispatcher is running alongside existing CI while we validate it. You can ignore this report and its statuses. Existing CI remains the merge signal.

  2/2 jobs
✅ 2 passed · ❌ 0 failed

Batches

Batch	State	Jobs	Workflow
batch-01	✅ passed	2/2	run 35007751573

_{Dispatcher finished on 77c7427 — GitHub Run.}

[dd-octo-sts]

Validation Report

All 21 validations passed.

Show details

Validation	Description	Status
agent-reqs	Verify check versions match the Agent requirements file	✅
ci	Validate CI configuration and code coverage settings	✅
codeowners	Validate every integration has a CODEOWNERS entry	✅
config	Validate default configuration files against spec.yaml	✅
dep	Verify dependency pins are consistent and Agent-compatible	✅
http	Validate integrations use the HTTP wrapper correctly	✅
imports	Validate check imports do not use deprecated modules	✅
integration-style	Validate check code style conventions	✅
jmx-metrics	Validate JMX metrics definition files and config	✅
labeler	Validate PR labeler config matches integration directories	✅
legacy-signature	Validate no integration uses the legacy Agent check signature	✅
license-headers	Validate Python files have proper license headers	✅
licenses	Validate third-party license attribution list	✅
metadata	Validate metadata.csv metric definitions	✅
models	Validate configuration data models match spec.yaml	✅
openmetrics	Validate OpenMetrics integrations disable the metric limit	✅
package	Validate Python package metadata and naming	✅
qa-label	Validate the pull request declares whether it needs QA for the next Agent release	✅
readmes	Validate README files have required sections	✅
saved-views	Validate saved view JSON file structure and fields	✅
version	Validate version consistency between package and changelog	✅

View full run

[dd-octo-sts]

Disk usage change

Commit 4806e52 compared against 77c7427.

No integration or dependency changed size.

[cit-pr-commenter-54b7da]

evalya-impact-summary

evalya impact analysis

Impact analysis: 0 selected, 0 skipped (of 0 test tasks)
Publish tasks:   2 (always emitted)
Diff (1 file):
  external_dns/tests/test_unit.py

Debug a specific task: evalya plan impact --path <path> --task <task>

Learn more about CI impact filtering