testIsAllNonNbspWhiteSpace() {
    const wsNode = document.createTextNode(' \t\r\n');
    assertTrue(
        'String is all non nbsp', editorNode.isAllNonNbspWhiteSpace(wsNode));
    const textNode = document.createTextNode('Hello');
    assertFalse(
        'String should not be whitespace',
        editorNode.isAllNonNbspWhiteSpace(textNode));
    const nbspNode = document.createTextNode('\u00a0');
    assertFalse('String has nbsp', editorNode.isAllNonNbspWhiteSpace(nbspNode));
  }
Test that isAllNonNbspWhiteSpace returns true if node contains only
whitespace that is not nbsp and false otherwise