}

  public void testMapSplitter_emptySeparator() {
    assertThrows(IllegalArgumentException.class, () -> COMMA_SPLITTER.withKeyValueSeparator(""));
  }

  public void testMapSplitter_malformedEntry() {
    assertThrows(
        IllegalArgumentException.class,
        () -> COMMA_SPLITTER.withKeyValueSeparator("=").split("a=1,b,c=2"));
  }

  /**