Prepender prepender = delegate.invoke(null, "a", 1);
    assertThat(prepender.prefix).isEqualTo("a");
    assertEquals(1, prepender.times);
  }

  public void testConstructor_returning() throws Exception {
    Invokable<?, Prepender> delegate =
        Prepender.constructor(String.class, int.class).returning(Prepender.class);
    Prepender prepender = delegate.invoke(null, "a", 1);