}

  public void testToString_present() {
    assertThat(Optional.of("training").toString()).isEqualTo("Optional.of(training)");
  }

  public void testPresentInstances_allPresent() {
    List<Optional<String>> optionals =
        ImmutableList.of(Optional.of("a"), Optional.of("b"), Optional.of("c"));
    assertThat(Optional.presentInstances(optionals)).containsExactly("a", "b", "c").inOrder();