public void isEmpty() {
    if (!checkNotNull(actual).isEmpty()) {
      failWithActual(simpleFact("expected to be empty"));
    }
  }
@Test
  public void tableIsEmptyWithFailure() {
    ImmutableTable<Integer, Integer, Integer> table = ImmutableTable.of(1, 5, 7);
    expectFailureWhenTestingThat(table).isEmpty();
    assertFailureKeys("expected to be empty", "but was");
  }