Has anyone succeeded in generating code coverage for Go unit tests? I can't find a tool for that on the web.
One major new feature of
go testis that it can now compute and, with help from a new, separately installed "
go tool cover" program, display test coverage results.
covertool is part of the
go.toolssubrepository. It can be installed by running
$ go get golang.org/x/tools/cmd/cover
The cover tool does two things.
First, when "
go test" is given the
-coverflag, it is run automatically to rewrite the source for the package and insert instrumentation statements. The test is then compiled and run as usual, and basic coverage statistics are reported:
$ go test -coverprofile fmtcoverage.html fmt ok fmt 0.060s coverage: 91.4% of statements $
Second, for more detailed reports, different flags to "go test" can create a coverage profile file, which the cover program, invoked with "
go tool cover", can then analyze.
The latest versions of Go (2013/09/19) use:
go test -coverprofile <filename> <package name>
Details on how to generate and analyze coverage statistics can be found by running the commands
$ go help testflag $ go tool cover -help
go test -coverprofile cover.outand then
go tool cover -html=cover.outopens
cover.outin your default browser
I don't even want to wait for the browser to open, so I defined this alias:
alias gc=grep -v -e " 1$" cover.out
That I just type
gc, and have a list of all the lines not yet covered (here: with a
coverage.outline not ending with "
Update 2022, possibly for Go 1.19
While the existing "
go test" based coverage workflow will continue to be supported, the proposal is to add coverage as a new build mode for "
In the same way that users can build a race-detector instrumented executable using "
go build -race", it will be possible to build a coverage-instrumented executable using "
go build -cover".
Merging coverage profiles produced in different GOOS/GOARCH environments will be supported.
Update March 2023, Go 1.20: "Code coverage for Go integration tests" shows that you can now build coverage-instrumented programs using “go build -cover”, then feed these instrumented binaries into an integration test to extend the scope of coverage testing.