TiDB Test Diff Triage

Trigger

Use this workflow when:

• A test diff appears, but touched code in the PR does not explain that behavior change.
• A single test run and full-suite run produce different outputs.
• Planner/executor testdata changed unexpectedly after merge/rebase.

Rule 1: rule out failpoint setup first

In TiDB, many test behaviors rely on failpoint instrumentation. -tags=intest,deadlock does not enable failpoints.

• Use docs/agents/testing-flow.md -> Failpoint decision for unit tests against the affected package.
• If any hit exists, rerun with Failpoint-enabled run and add -count=1 to the go test command for reproducibility.
• If the diff disappears after failpoint enable, classify it as an environment/setup issue instead of a logic regression.

Rule 2: isolate merge impact