assertEquals(underlying.size(), map.size());
    assertFalse(map.containsKey("c"));

    underlying.clear();
    assertEquals(underlying.size(), map.size());
  }

  public void testTransformChangesAreReflectedInUnderlyingMap() {
    Map<String, Integer> underlying = new LinkedHashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    underlying.put("d", 4);