ImmutableMap.copyOf(Collections.<String, Integer>emptyMap());
    assertEquals(Collections.<String, Integer>emptyMap(), copy);
    assertSame(copy, ImmutableMap.copyOf(copy));
  }

  public void testCopyOfSingletonMap() {
    ImmutableMap<String, Integer> copy = ImmutableMap.copyOf(singletonMap("one", 1));
    assertMapEquals(copy, "one", 1);
    assertSame(copy, ImmutableMap.copyOf(copy));
  }