assertThat(mapCache.put("key", "new value")).isEqualTo("value");
    assertThat(mapCache.get("key")).isEqualTo("new value");
  }

  @Test
  public void testRemoveEqualKeyWithDifferentReference() {
    String fooReference1 = new String("foo");
    String fooReference2 = new String("foo");
    assertThat(fooReference1).isNotSameInstanceAs(fooReference2);