func TestExitCodeMissing(t *testing.T) {
	var wantErr *regexp.Regexp
	check := func(text string) {
		t.Helper()
		var out strings.Builder
		f, exitStr := newExitCodeFilter(&out)
		if want := "exitcode="; want != exitStr {
			t.Fatalf("test assumes exitStr will be %q, but got %q", want, exitStr)
		}
		f.Write([]byte(text))
		_, err := f.Finish()
		// We should get a no exit code error
		if err == nil || !wantErr.MatchString(err.Error()) {