assertFalse(map.remove("bar", 1));
    assertEquals(Integer.valueOf(1), map.get("foo"));
    assertTrue(map.remove("foo", 1));
    assertTrue(map.isEmpty());
  }

  public void testReplace() {
    TestMap map = new TestMap();
    map.put("foo", 1);
    assertEquals(Integer.valueOf(1), map.replace("foo", 2));
    assertNull(map.replace("bar", 3));
    assertEquals(Integer.valueOf(2), map.get("foo"));