go-cov

go-cov

Generate coverage profiles with the ability to explicitly exclude lines, inspired by the exclusion functionality of coverage.py.

Having a coverage report that excludes lines you don't intend to cover can be helpful in maintaining test coverage, since it makes adding code not covered by tests a conscious decision. Knowing what you do/do not intend to cover with tests is also useful for example when looking back over old code and trying to determine why something may not already be covered by tests.

It also allows you to aim to have 100% coverage without having to cover every single line. This is then much easier to maintain without any extra tooling: just make sure coverage is always 100%.

Excluding Lines

Blocks can be excluded by adding a //go-cov:skip comment at the start of the block:

func unTestable() { //go-cov:skip
    // do stuff...
}

func someFunc(debug bool) {
    // do stuf...

    // the comment doesn't need to start with the skip
    if debug { //some-other-tool:blah //go-cov:skip
        log.Println("This is some useful debug information")
    }

    if someHardToTestCondition { //go-cov:skip // explaination for not testing this
    }
}

Usage

Update coverage profile with skips

Takes a coverage profile (i.e. one generated with go test -coverprofile) and adds coverage for any blocks starting with a go-cov:skip comment. The result is written to stdout. Sample usage:

# generate the coverage profile
$ go test -coverprofile=coverage.out ./...
# write the updated profile to `go-cov.out`
$ go-cov add-skips coverage.out > go-cov.out
# investigate the result
$ go tool cover -func=go-cov.out

Report coverage

The report command reports coverage in a human readable manner and can optionally fail if coverage is below a required level. Sample usage:

$ go-cov report coverage.out
# fail if less than 80% of lines are covered
$ go-cover report --fail-under 80 coverage.out
# the coverage profiles can be read from stdin
$ go-cover add-skips coverage.out | go-cover report --fail-under 90