t.Fatalf("marshaling of nil failed: %s", err)
	}
	got := string(b)
	want := "null"
	if got != want {
		t.Fatalf("marshaling of nil failed: got %s want %s", got, want)
	}
}

func TestIntXMLEncoding(t *testing.T) {
	for _, test := range encodingTests {
		for _, sign := range []string{"", "+", "-"} {
			x := sign + test
			var tx Int
			tx.SetString(x, 0)
			b, err := xml.Marshal(&tx)