@Test
public void testNestableBlockComment() {

  Parser<Void> scanner = Scanners.nestableBlockComment("/*", "*/");
  assertEquals("nestable block comment", scanner.toString());
  assertNull(scanner.parse("/* not nested */"));
  assertNull(scanner.parse("/* this is /*nested*/ */"));
  assertFailure(mode, scanner, "", 1, 1);
  assertFailure(mode, scanner, "/*", 1, 3);
  assertFailure(mode, scanner, "/* /**/", 1, 8);
  assertFailure(mode, scanner, "/* /**/*", 1, 9);
}