@Test
public void childNumberTest() {

    Path el = childNumber(1).ofType(span.withClass("a"));
    NodeList nodes = findAllByXpath("<span></span><span class='a x'>a<span class='a y'>b</span><span class='a z'>c</span></span>", el);
    assertThat(nodes.getLength(), equalTo(2));
    assertThat(getCssClass(nodes.item(0)), equalTo("a x"));
    assertThat(getCssClass(nodes.item(1)), equalTo("a y"));
    assertThat(el.toString(), equalTo("child number 1 of type(span, that has class a)"));
}