testGetFirstChild() {
    setUpDomTree();

    assertNull('Has no none ws children', editorNode.getFirstChild(childNode2));
    assertEquals(
        'Should skip first child, as it is ws', gChildMixedNode1,
        editorNode.getFirstChild(childNode1));
    assertEquals(
        'Should just return first child', gChildTextNode3a,
        editorNode.getFirstChild(childNode3));
    assertEquals(
        'Should return first child', childNode1,
        editorNode.getFirstChild(parentNode));

    assertNull(
        'First child of a text node should return null',
        editorNode.getFirstChild(gChildTextNode1));
    assertNull(
        'First child of null should return null',
        editorNode.getFirstChild(null));

    tearDownDomTree();
  }
Creates a DOM tree and tests that getFirstChild properly ignores
ignorable nodes