@Test
	public void testAltsWithLabels() throws Exception {
		LexerGrammar lg = new LexerGrammar(lexerText);
		Grammar g = new Grammar(
			"parser grammar T;\n" +
			"s : ID  # foo\n" +
			"  | INT # bar\n" +
			"  ;\n",
			lg);
		// it won't show the labels here because my simple node text provider above just shows the alternative
		testInterp(lg, g, "s", "a",		"(s:1 a)");
		testInterp(lg, g, "s", "3", 	"(s:2 3)");
	}
Tests to ensure GrammarParserInterpreter subclass of ParserInterpreter
 hasn't messed anything up.
tool-testsuite/test/org/antlr/v4/test/tool/TestGrammarParserInterpreter.java