assertEquals(OptionalDouble.empty(), ArbitraryInstances.get(OptionalDouble.class));
    assertThat(ArbitraryInstances.get(UUID.class)).isNotNull();
  }

  public void testGet_collections() {
    assertEquals(ImmutableSet.of().iterator(), ArbitraryInstances.get(Iterator.class));
    assertFalse(ArbitraryInstances.get(PeekingIterator.class).hasNext());

    assertEquals(0, ArbitraryInstances.get(Number.class));
    assertEquals(UTF_8, ArbitraryInstances.get(Charset.class));
    assertThat(ArbitraryInstances.get(UUID.class)).isNotNull();
  }

  public void testGet_collections() {
    assertEquals(ImmutableSet.of().iterator(), ArbitraryInstances.get(Iterator.class));
    assertFalse(ArbitraryInstances.get(PeekingIterator.class).hasNext());