testing: TestRaceReports failures

[gopherbot]

#!watchflakes
default <- pkg == "testing" && test == "TestRaceReports"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestRaceReports
    testing_test.go:509: /home/swarming/.swarming/w/ir/x/t/go-build459919634/b886/testing.test -test.run=^TestRaceReports$ -test.bench=TestRaceReports -test.v -test.parallel=2 -test.benchtime=2x: <nil>
        === RUN   TestRaceReports
        === RUN   TestRaceReports/Sub
        --- PASS: TestRaceReports (0.00s)
            --- PASS: TestRaceReports/Sub (0.00s)
        PASS
    testing_test.go:518: got 0 race reports, want 1
--- FAIL: TestRaceReports (1.04s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "testing" && test == "TestRaceReports"

2026-06-18 15:05 go1.27-freebsd-amd64-race release-branch.go1.27@ac2b8fc0 testing.TestRaceReports (log)

=== RUN   TestRaceReports
    testing_test.go:509: /home/swarming/.swarming/w/ir/x/t/go-build459919634/b886/testing.test -test.run=^TestRaceReports$ -test.bench=TestRaceReports -test.v -test.parallel=2 -test.benchtime=2x: <nil>
        === RUN   TestRaceReports
        === RUN   TestRaceReports/Sub
        --- PASS: TestRaceReports (0.00s)
            --- PASS: TestRaceReports/Sub (0.00s)
        PASS
    testing_test.go:518: got 0 race reports, want 1
--- FAIL: TestRaceReports (1.04s)

— watchflakes

[ipezygj]

C:/Program Files/Git/claim - Will submit PR

[JunyangShao]

@adonovan @neild