assertThat(impliedFeatures(features)).isNotSameInstanceAs(features);
  }

  public void testImpliedFeatures_returnsImpliedFeatures() {
    assertThat(impliedFeatures(newHashSet(FOO))).isEmpty();

    assertThat(impliedFeatures(newHashSet(IMPLIES_IMPLIES_FOO))).containsExactly(IMPLIES_FOO, FOO);

    assertThat(impliedFeatures(newHashSet(IMPLIES_IMPLIES_FOO_AND_IMPLIES_BAR)))

    assertThat(impliedFeatures(features)).isNotSameInstanceAs(features);
  }

  public void testImpliedFeatures_returnsImpliedFeatures() {
    assertThat(impliedFeatures(newHashSet(FOO))).isEmpty();

    assertThat(impliedFeatures(newHashSet(IMPLIES_IMPLIES_FOO))).containsExactly(IMPLIES_FOO, FOO);

    assertThat(impliedFeatures(newHashSet(IMPLIES_IMPLIES_FOO_AND_IMPLIES_BAR)))

   * of them.
   *
   * @param features the set of features whose implications to find
   * @return the implied set of features
   */
  public static Set<Feature<?>> impliedFeatures(Set<Feature<?>> features) {
    Set<Feature<?>> impliedSet = new LinkedHashSet<>();
    Queue<Feature<?>> queue = new ArrayDeque<>(features);
    while (!queue.isEmpty()) {
      Feature<?> feature = queue.remove();