testing: TestTBHelper fails if run with -failfast

[bcmills]

What version of Go are you using (go version)?

~$ go1.21rc2 version
go version go1.21rc2 linux/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/usr/local/google/home/bcmills/.cache/go-build'
GOENV='/usr/local/google/home/bcmills/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/usr/local/google/home/bcmills/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/usr/local/google/home/bcmills'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/google/home/bcmills/sdk/go1.21rc2'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/google/home/bcmills/sdk/go1.21rc2/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.21rc2'
GCCGO='/usr/bin/gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2889092914=/tmp/go-build -gno-record-gcc-switches'

What did you do?

go1.21rc2 test testing -failfast

What did you expect to see?

Test passing.

What did you see instead?

--- FAIL: TestTBHelper (0.00s)
    helper_test.go:52: got output:
        
        --- FAIL: Test (?s)
        helperfuncs_test.go:12: 0
        helperfuncs_test.go:40: 1
        helperfuncs_test.go:21: 2
        helperfuncs_test.go:42: 3
        helperfuncs_test.go:49: 4
        --- FAIL: Test/sub (?s)
        helperfuncs_test.go:52: 5
        helperfuncs_test.go:21: 6
        helperfuncs_test.go:51: 7
        helperfuncs_test.go:63: 8
        helperfuncs_test.go:82: recover 12
        helperfuncs_test.go:84: GenericFloat64
        helperfuncs_test.go:85: GenericInt
        helperfuncs_test.go:71: 9
        helperfuncs_test.go:67: 10
        
        want:
        
        --- FAIL: Test (?s)
        helperfuncs_test.go:12: 0
        helperfuncs_test.go:40: 1
        helperfuncs_test.go:21: 2
        helperfuncs_test.go:42: 3
        helperfuncs_test.go:49: 4
        --- FAIL: Test/sub (?s)
        helperfuncs_test.go:52: 5
        helperfuncs_test.go:21: 6
        helperfuncs_test.go:51: 7
        helperfuncs_test.go:63: 8
        --- FAIL: Test/sub2 (?s)
        helperfuncs_test.go:78: 11
        helperfuncs_test.go:82: recover 12
        helperfuncs_test.go:84: GenericFloat64
        helperfuncs_test.go:85: GenericInt
        helperfuncs_test.go:71: 9
        helperfuncs_test.go:67: 10
FAIL
FAIL	testing	0.007s
FAIL

[gopherbot]

Change https://go.dev/cl/506955 mentions this issue: testing: use subprocesses in TestTBHelper and TestTBHelperParallel