Get golang coverage programmatically

Question

The go -cover or -coverprofile is great when running go tests and can show nicely in html or plain text. But is there an api to access it programmatically or process the file?

Answer 1

You can try axw/gocov, which:

• will run test with a -coverprofile argument
• parse the results (gocov/convert.go)

You can see a tool like GoCov GUI uses gocov.Statement in convert_statements(s []*gocov.Statement, offset int) in order to build a small GUI:

Answer 2

Let us assume that we want to obtain test coverage percentage (as float64) on a project that we dynamically fetch from a git repo from somewhere, and store in the current folder under "_repos/src". The input would be the project in a typical "go get" format. We need to execute "go test -cover", with the properly GOPATH variable set, parse the output, and extract the actual percentage of the test coverage. With the current Go 1.9 testing tool, the code below achieves that.

// ParseFloatPercent turns string with number% into float.
func ParseFloatPercent(s string, bitSize int) (f float64, err error) {
    i := strings.Index(s, "%")
    if i < 0 {
        return 0, fmt.Errorf("ParseFloatPercent: percentage sign not found")
    }
    f, err = strconv.ParseFloat(s[:i], bitSize)
    if err != nil {
        return 0, err
    }
    return f / 100, nil
}

// GetTestCoverage returns the tests code coverage as float
// we are assuming that project is a string
// in a standard "Go get" form, for example:
//     "github.com/apache/kafka"
// and, that you have cloned the repo into "_repos/src"
// of the current folder where your executable is running.
//
func GetTestCoverage(project string) (float64, error) {
    cmdArgs := append([]string{"test", "-cover"}, project)
    cmd := exec.Command("go", cmdArgs...)
    // get the file absolute path of our main executable
    dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
    if err != nil {
        log.Println(err)
        return 0, err
    }
    // set the GOPATH for tests to work
    cmd.Env = os.Environ()
    cmd.Env = append(cmd.Env, "GOPATH="+dir+"/_repos/")

    var out []byte
    cmd.Stdin = nil
    out, err = cmd.Output()

    if err != nil {
        fmt.Println(err.Error())
        return 0, err
    }

    r := bufio.NewReader(bytes.NewReader(out))
    // first line from running "go test -cover" should be in a form
    // ok   <project>   6.554s  coverage: 64.9% of statements
    // split with /t and <space> characters
    line, _, err := r.ReadLine()

    if err != nil {
        fmt.Println(err.Error())
        return 0, err
    }

    parts := strings.Split(string(line), " ")
    if len(parts) < 6 {
        return 0, errors.New("go test -cover do not report coverage correctly")
    }
    if parts[0] != "ok" {
        return 0, errors.New("tests do not pass")
    }
    f, err := ParseFloatPercent(parts[3], 64)
    if err != nil {
        // the percentage parsing problem
        return 0, err
    }

    return f, nil
}