Number zero = map.getInstance(Number.class);
    assertEquals(0, zero);

    Double pi = map.getInstance(Double.class);
    assertThat(pi).isEqualTo(Math.PI);
  }

  public void testPrimitiveAndWrapper() {
    ImmutableClassToInstanceMap<Number> ictim =
        new ImmutableClassToInstanceMap.Builder<Number>()
            .put(Integer.class, 0)
            .put(int.class, 1)
            .build();