testing - 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 os.Exit(1) the tests fail.

package main

import (
    "log"
)

func hello() {
    log.Print("Hello!")
}

func goodbye() {
    log.Fatal("Goodbye!")
}

func init() {
    log.SetFlags(0)
}

func main() {
    hello()
    goodbye()
}

Here are the hypothetical tests:

package main

import (
    "bytes"
    "log"
    "testing"
)


func TestHello(t *testing.T) {
    var buf bytes.Buffer
    log.SetOutput(&buf)

    hello()

    wantMsg := "Hello!
"
    msg := buf.String()
    if msg != wantMsg {
        t.Errorf("%#v, wanted %#v", msg, wantMsg)
    }
}

func TestGoodby(t *testing.T) {
    var buf bytes.Buffer
    log.SetOutput(&buf)

    goodbye()

    wantMsg := "Goodbye!
"
    msg := buf.String()
    if msg != wantMsg {
        t.Errorf("%#v, wanted %#v", msg, wantMsg)
    }
}

Answer 1

Waitting for answers