tt.fn()
		}()
		if got := <-didPanic; got != tt.wantPanic {
			t.Errorf("%s: panicked = %v; want %v", tt.name, got, tt.wantPanic)
		}
	}
}

func TestBuilderWriteInvalidRune(t *testing.T) {
	// Invalid runes, including negative ones, should be written as
	// utf8.RuneError.
	for _, r := range []rune{-1, utf8.MaxRune + 1} {
		var b Builder
		b.WriteRune(r)