chore: add TCP handler and warmup tests

[PhantomInTheWire]

Summary by CodeRabbit

• Tests
  • Added test coverage for resolver warmup logic, including root server queries and delegation cache population.
  • Added comprehensive test suite for TCP DNS handler, covering basic queries, error handling, message validation, and query counting.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a720fd7 and 261b5ad.

📒 Files selected for processing (2)

• internal/resolver/warmup_test.go
• internal/server/tcp_test.go

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📝 Walkthrough

Walkthrough

Two new test files are introduced: one for resolver warmup logic featuring a mockTransport struct to simulate DNS queries, and another for TCP DNS handler with a mockResolver to test various query scenarios and error conditions.

Changes

Cohort / File(s)	Summary
Resolver Warmup Tests internal/resolver/warmup_test.go	Adds mockTransport struct implementing the Transport interface to simulate DNS queries. Includes three tests validating RTT probing of root servers, delegation cache population, and context cancellation behavior.
TCP Handler Tests internal/server/tcp_test.go	Adds mockResolver struct for testing and helper utilities (writeTCPQuery, readTCPResponse, makeTestQuery, makeTestResponse). Includes five tests covering basic queries, resolver errors, invalid message sizes, pipelined queries, and query counting.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A rabbit hops through test files bright,
Mock transports and resolvers take flight!
TCP streams and warmup flows,
Coverage grows as the test suite glows! ✨

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch test/tcp-warmup

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