How to test Go function containing log.Fatal()

Question

Say, I had the following code that prints some log messages. How would I go about testing that the correct messages have been logged? As log.Fatal calls o

Answer 1

If you're using logrus, there's now an option to define your exit function from v1.3.0 introduced in this commit. So your test may look something like:

func Test_X(t *testing.T) {
    cases := []struct{
        param string
        expectFatal bool
    }{
        {
            param: "valid",
            expectFatal: false,
        },
        {
            param: "invalid",
            expectFatal: true,
        },
    }

    defer func() { log.StandardLogger().ExitFunc = nil }()
    var fatal bool
    log.StandardLogger().ExitFunc = func(int){ fatal = true }

    for _, c := range cases {
        fatal = false
        X(c.param)
        assert.Equal(t, c.expectFatal, fatal)
    }
}