package main import ( "testing" ) type Error struct { errCode uint8 } func (e *Error) Error() string { switch e.errCode { case 1: return "file not found" case 2: return "time out" case 3: return "permission denied" default: return "unknown error" } } func checkError(err error) { if err != nil { panic(err) } } func TestStart( t *testing.T) { var e *Error checkError(e) }