assertThrows(NullPointerException.class, () -> ImmutableMap.of(null, 1));

    assertThrows(NullPointerException.class, () -> ImmutableMap.of("one", 1, null, 2));
  }

  public void testOfNullValue() {
    assertThrows(NullPointerException.class, () -> ImmutableMap.of("one", null));

    assertThrows(NullPointerException.class, () -> ImmutableMap.of("one", 1, "two", null));
  }