script.go

var testPRMessageTests = []struct {
	message  string
	expected error
}{
	{"Merge pull request #4 in ABC/def from some_branch to master\n\nMerge comment\n\n* commit '1h2e09d3029370d92723'", nil},
	{"Merge pull request #4 in ABC/def from some_branch to master\n", %%%WHAT_COMES_HERE%%%},
}

func TestTestPRMessage(t *testing.T) {
	for _, test := range testPRMessageTests {
		actual := testPRMessage(test.message)
		if actual != test.expected {
			t.Errorf("getPRMessage(%s) - expected: %s, actual: %s", test.message, test.expected, actual)
		}
	}
}

script_test.go

func testPRMessage(gitMessage string) error {
	//var err error
	if len(strings.Split(gitMessage, "\n")) < 3 {
		return errors.New("Malformated pull request. Cannot find merge comment.")
	}
	return nil
}