} else {
      assertThrows(UnsupportedOperationException.class, () -> map.put(keyToPut, valueToPut));
    }
    assertInvariants(map);
  }

  public void testPutNullKey() {
    if (!supportsPut) {
      return;
    }
    Map<K, V> map = makeEitherMap();
    V valueToPut;
    try {
      valueToPut = getValueNotInPopulatedMap();