codecov-go-example

By default, there is a discrepancy in computation of coverage by Codecov.io and the coverage reported by go test -covermode=atomic.

This is because of the way go test ... reports coverage; for if statements:

   if Condition() {
     DoSomething()
   }

it includes the trailing { at end of line containig the if Condition() into the next statement DoSomething(). This means that if Condition() evaluates to false, you have a partial hit on this line. Additionally, go test ... still keeps track of statements covered, regardless of the lines hit, while Codecov tracks lines.

The output of both tools can differ widely due to that. At my company, which uses a large codebase, we have more that 10% in coverage difference reported by both tools on some packages.

I used this repository to experiment with different solutions.

Obtaining coverage with GO tools

$ go test -race -covermode=atomic -coverprofile=coverage.txt .
ok  	github.com/sbougerel/codecov-go-example	1.016s	coverage: 50.0% of statements

The generated coverage file contents are:

mode: atomic
github.com/sbougerel/codecov-go-example/main.go:5.44,6.8 1 1
github.com/sbougerel/codecov-go-example/main.go:10.2,10.8 1 1
github.com/sbougerel/codecov-go-example/main.go:14.2,14.13 1 0
github.com/sbougerel/codecov-go-example/main.go:6.8,8.3 1 0
github.com/sbougerel/codecov-go-example/main.go:10.8,12.3 1 1
github.com/sbougerel/codecov-go-example/main.go:17.13,19.2 1 0

Prefered way to push coverage to Codecov.

After exprimentation, I found that using CoberturaXML format yields the best match to runing go test ... and most importantly, shows on Codecov what one would expect of the coverage of its files.

Get external utilities:

$ go get github.com/axw/gocov/...
$ go get github.com/AlekSi/gocov-xml

After the output of go test ... above, run:

$ gocov convert coverage.txt | gocov-xml > coverage.xml

Then push this new XML file to Codecov.

bash <(curl -s https://codecov.io/bash) -f coverage.xml

See coverage results on Codecov.io.

Results

As can be seen above, the GO tool reports that 50% of statements are covered, and same for Codecov.io. For more visual evidance that the coverage is reported are similar, you can run, on the original coverage.txt

go tool cover -html coverage.txt

Conclusion

This method is the one currently in use in my company.