assertTrue(map.containsValue(valueToPut));
    } else {
      assertThrows(RuntimeException.class, () -> map.put(null, valueToPut));
    }
    assertInvariants(map);
  }

  public void testPutNullValue() {
    if (!supportsPut) {
      return;
    }
    Map<K, V> map = makeEitherMap();
    K keyToPut;
    try {
      keyToPut = getKeyNotInPopulatedMap();