assertEquals("", Strings.commonPrefix("xyz", "abcde"));
    assertEquals("", Strings.commonPrefix("xyz", "abcxyz"));
    assertEquals("a", Strings.commonPrefix("abc", "aaaaa"));
    assertEquals("aa", Strings.commonPrefix("aa", "aaaaa"));
    assertEquals("abc", Strings.commonPrefix(new StringBuilder("abcdef"), "abcxyz"));

    // Identical valid surrogate pairs.
    assertEquals(

  private static final String ALMOST_TOO_MANY_LEVELS = Strings.repeat("a.", 127);

  @SuppressWarnings("InlineMeInliner") // String.repeat unavailable under Java 8
  private static final String ALMOST_TOO_LONG = Strings.repeat("aaaaa.", 40) + "1234567890.c";

  private static final ImmutableSet<String> VALID_NAME =
      ImmutableSet.of(
          // keep-sorted start
          "123.cn",
          "8server.shop",
          "a" + DELTA + "b.com",

    tester.testAllPublicInstanceMethods(matcher);
  }

  public void testNoMatches() {
    doTestNoMatches(CharMatcher.none(), "blah");
    doTestNoMatches(is('a'), "bcde");
    doTestNoMatches(isNot('a'), "aaaa");
    doTestNoMatches(anyOf(""), "abcd");
    doTestNoMatches(anyOf("x"), "abcd");
    doTestNoMatches(anyOf("xy"), "abcd");
    doTestNoMatches(anyOf("CharMatcher"), "zxqy");