@Test
public void shouldIndicateAbsenceOfSubstring() {

	Assert.assertEquals(-1, new TextNode("abcdef").indexOf(new TextNode("cdefg")));
	Assert.assertEquals(-1, new TextNode("abcdef").indexOf(new TextNode("ac")));
	Assert.assertEquals(-1, new TextNode("abcdef").indexOf(new TextNode("xab")));
	Assert.assertEquals(-1, new TextNode("abcdef").indexOf(new TextNode("cdf")));
}