public void testPutUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> multimap().put(k3(), v3()));
  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPutEmpty() {
    int size = getNumElements();

    assertGet(k3(), ImmutableList.of());

    assertTrue(multimap().put(k3(), v3()));

    assertGet(k3(), v3());
    assertEquals(size + 1, multimap().size());
  }