@Test
public void testInvalidVoiceModeHeader() {

    final StringBuilder builder = new StringBuilder();
    builder.append("<?xml version=\"1.0\" ?>");
    builder.append("<grammar version=\"1.0\" ");
    builder.append(" xmlns=\"http://www.w3.org/2001/06/grammar\" ");
    builder.append(" mode=\"voice\"></grammar>");
    final GrammarDocument doc =
        GrammarUtil.getGrammarFromString(builder.toString());
    final GrammarType type = identifier.identify(doc);
    Assert.assertNull(type);
}