How to test os.exit scenarios in Go

Question

Given this code

func doomed() {
  os.Exit(1)
}

How do I properly test that calling this function will result in an exit using go test

Answer 1

I do this by using bouk/monkey:

func TestDoomed(t *testing.T) {
  fakeExit := func(int) {
    panic("os.Exit called")      
  }
  patch := monkey.Patch(os.Exit, fakeExit)
  defer patch.Unpatch()
  assert.PanicsWithValue(t, "os.Exit called", doomed, "os.Exit was not called")
}

monkey is super-powerful when it comes to this sort of work, and for fault injection and other difficult tasks. It does come with some caveats.