testing: Coverage() function doesnt work for go 1.20+

[jehowell]

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

$ go version
go version go1.20.3 linux/arm64

Does this issue reproduce with the latest release?

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

go env Output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN="/go/bin"
GOCACHE="/home/vscode/.cache/go-build"
GOENV="/home/vscode/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_arm64"
GOVCS=""
GOVERSION="go1.20.3"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/workspaces/work/go.mod"
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 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2929308236=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Calling testing.Coverage() always returns 0.0. Looking at the source, this function has not been updated to the new coverage2 system.

What did you expect to see?

testing.Coverage() should return the percent of code coverage for the current unit test.

What did you see instead?

Always returns 0

[ianlancetaylor]

CC @thanm

[thanm]

Thanks for the report. testing.Coverage() is definitely something that slipped through the cracks (it currently has no unit tests); I'll add this to my other cleanup items for code coverage this release.

[jehowell]

Awesome thanks! In addition, it would be great if that value Coverage() returns is the same as the one that gets sent to the coverage report after the test. The previous implementation did not calculate this value the same way so the value returned differed from the coverage report (% of blocks vs % of statements).

We use this value as a pseudo way to enforce test coverage. Would love to see this more integrated into the tools in the future to do this in a more official way.

[thanm]

Thanks. I'll put that issue on my list. Cheers, Than

…

On Wed, Apr 26, 2023 at 2:08 PM Simon Kotwicz ***@***.***> wrote: @thanm <https://github.com/thanm> may not be related but Go 1.20 broke overall code coverage for a lot of people as per #24570 (comment) <#24570 (comment)> — Reply to this email directly, view it on GitHub <#59590 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AC5WC3B4CAYIG3VKKPFIN63XDFQC5ANCNFSM6AAAAAAW4GMIDU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[gopherbot]

Change https://go.dev/cl/495450 mentions this issue: cmd/go,testing: re-implement testing.Coverage

[gopherbot]

Change https://go.dev/cl/495449 mentions this issue: runtime/coverage: add coverage snapshot helper routine

[lbergesio]

Hi! I was expecting this to be backported to 1.20.5 but it was not. I saw the commit is in release-branch.go1.21 but not in 1.21.rc2- Is it planned to be backported to 1.20.6? In 1.20.x this is totally broken. Thaks!

[thanm]

From https://github.com/golang/go/wiki/MinorReleases:

Our default decision should always be to not backport, but fixes for security issues, serious problems with no workaround, and documentation fixes are backported to the most recent two release branches, if applicable to that branch

Generally speaking "serious problem" means your program is crashing or computing incorrect results, that sort of thing. I would be surprised in this case if the release team were to approve a backport given the nature of the bug. Sorry about that.

[lbergesio]

So, testing.Coverage() is returning 0 always, is not that an incorrect computing result?. My program is not crashing but my test suite is.

So I need the build -cover feature introduced in 1.20 but can't break my test suite. I was just asking if I can expect this to be fixed in 1.20.x, otherwise I will wait to 1.21