os: TestRemoveAllDotDot broken at head

[bcmills]

Observed in https://build.golang.org/log/79c45622d3e12177863a8eafbb8772e26af1a30c.

Broken in https://golang.org/cl/171099 (#29921), and the breakage in the longtest builder was masked by #31263.

[bcmills]

And some others too:

~/go/src/os$ go test .
--- FAIL: TestRemoveAllDotDot (0.00s)
    removeall_test.go:252: unlinkat /tmp/TestRemoveAllDotDot-695588954/x/y: error from RemoveAllTestHook
--- FAIL: TestRemoveUnreadableDir (0.00s)
    removeall_test.go:406: openfdat /tmp/TestRemoveAllButReadOnly-192841201/d0/d1/d2: permission denied
--- FAIL: TestRemoveAllButReadOnlyAndPathError (0.00s)
    removeall_test.go:360: got "/tmp/TestRemoveAllButReadOnly-172665500/a/x/1", expected pathErr.path "/tmp/TestRemoveAllButReadOnly-172665500/b/y"
FAIL
FAIL    os      18.322s

[gopherbot]

Change https://golang.org/cl/171777 mentions this issue: os: fix aliasing bug in RemoveAllTestHook restoration

[cuonglm]

@bcmills Thanks for the fix 👍

Can you tell my why trybot result and local test passed in my original CL?

[ianlancetaylor]

Because the tests are run in short mode by default, and your test wasn't run in short mode.

[cuonglm]

Because the tests are run in short mode by default, and your test wasn't run in short mode.

Ah right, but how can it pass in my local run? I just did go-tip test -v -count=1.

Is there a way I can make sure that my test will run all tests or mimic the builder so we won't get in this trouble next time?

[bcmills]

The os package resolves to whatever os package is present in the GOROOT of the go command (go-tip in your example), so if you built go-tip in a different GOROOT from the one in which you drafted the CL, then go-tip test os might have actually tested a copy of the os package without your changes.