test: stabilize TestClusterIDInReq

[lance6716]

close #1893

What

• keep TestClusterIDInReq on MockTikvService (no test simplification to pure stub)
• keep asserting ClusterId > 0 in the wrapped fnClient
• replace the fragile probe flow (SendReq + 10ms timeout) with:
  • a readiness wait via rpcClient.SendRequest + Eventually
  • a normal assertion request with time.Second timeout

Why

The old test path occasionally hit startup/timing races under -race, and could return a pseudo region error (EpochNotMatch) before the assertion path was stable.

Result

• still validates cluster-id propagation against MockTikvService
• avoids timing-sensitive false failures in CI
• verified with:
  • go test -race ./internal/locate -run TestRegionRequestToSingleStore/TestClusterIDInReq -count=300 -failfast
  • go test -race ./internal/locate

Summary by CodeRabbit

• Tests
  • Tightened assertions to be more precise and robust.
  • Replaced an ad-hoc readiness probe with a deterministic wait-before-run approach to start the test flow.
  • Overall improved test stability and reduced flakiness in request-timing scenarios.

[ti-chi-bot]

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[coderabbitai]

📝 Walkthrough

Walkthrough

Replace the explicit probe SendReq in TestClusterIDInReq with an Eventually readiness loop that retries SendRequest until the server loop is ready; change the ClusterId assertion to a greater-than-0 check and perform the final SendReq with a 1s timeout after readiness is observed.

Changes

Cohort / File(s)	Summary
Region request test internal/locate/region_request_test.go	Assert req.ClusterId > 0 (uint64); remove separate probe SendReq; add an Eventually/wait loop that retries SendRequest until server readiness; keep final SendReq with a 1s timeout. Timing/control-flow adjustments in the test.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

size/M, contribution

Suggested reviewers

• lcwangchao
• MyonKeminta

Poem

🐰
I waited patient, tiny paws in place,
No noisy probe to start the race.
Cluster IDs checked, the loop runs tight,
At last the request hops into light. 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'test: stabilize TestClusterIDInReq' directly and accurately summarizes the main change—stabilizing a flaky test.
Linked Issues check	✅ Passed	The PR fully addresses issue #1893 by replacing the fragile probe flow with an explicit readiness wait using Eventually and a stable assertion request, eliminating flakiness caused by startup/timing races.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to stabilizing TestClusterIDInReq; no unrelated modifications to other tests, production code, or unrelated functionality are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[Copilot]

Pull request overview

This PR stabilizes the TestClusterIDInReq test by removing its dependency on a real mock gRPC server and network timing. The test now uses a simple inline function stub to validate request metadata, making it deterministic and eliminating CI flakiness.

Changes:

• Replaced mock gRPC server setup with an inline fnClient stub
• Removed probe request and cleanup code that was causing timing-related flakiness
• Changed timeout from 10ms to 1 second since timeout behavior is no longer being tested

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