"nullness", // test of a bogus call
  })
  public void testRepeat_null() {
    assertThrows(NullPointerException.class, () -> Strings.repeat(null, 5));
  }

  @SuppressWarnings("UnnecessaryStringBuilder") // We want to test a non-String CharSequence
  public void testCommonPrefix() {
    assertThat(Strings.commonPrefix("", "")).isEqualTo("");
    assertThat(Strings.commonPrefix("abc", "")).isEqualTo("");

    "nullness", // test of a bogus call
  })
  public void testRepeat_null() {
    assertThrows(NullPointerException.class, () -> Strings.repeat(null, 5));
  }

  @SuppressWarnings("UnnecessaryStringBuilder") // We want to test a non-String CharSequence
  public void testCommonPrefix() {
    assertThat(Strings.commonPrefix("", "")).isEqualTo("");
    assertThat(Strings.commonPrefix("abc", "")).isEqualTo("");

        @Override
        public boolean apply(CharSequence input) {
          return (input.length() > 0) && (input.charAt(0) == 'a');
        }
      };

  @SuppressWarnings("UnnecessaryStringBuilder") // false positive in a weird case
  public void testIndexOf_genericPredicate() {
    List<CharSequence> sequences = new ArrayList<>();
    sequences.add("bob");
    sequences.add(new StringBuilder("charlie"));