}
  }

  public void testReplaceFrom() {
    assertEquals("yoho", is('a').replaceFrom("yaha", 'o'));
    assertEquals("yh", is('a').replaceFrom("yaha", ""));
    assertEquals("yoho", is('a').replaceFrom("yaha", "o"));
    assertEquals("yoohoo", is('a').replaceFrom("yaha", "oo"));
    assertEquals("12 > 5", is('>').replaceFrom("12 > 5", ">"));
  }

  public void testRetainFrom() {

    }
  }

  public void testReplaceFrom() {
    assertEquals("yoho", is('a').replaceFrom("yaha", 'o'));
    assertEquals("yh", is('a').replaceFrom("yaha", ""));
    assertEquals("yoho", is('a').replaceFrom("yaha", "o"));
    assertEquals("yoohoo", is('a').replaceFrom("yaha", "oo"));
    assertEquals("12 > 5", is('>').replaceFrom("12 > 5", ">"));
  }

  public void testRetainFrom() {

  private static class ConflictingRequirementsExampleDerivedInterfaceTester
      extends ExampleBaseInterfaceTester {}

  public void testTestFeatureEnums() throws Exception {
    // Haha! Let's test our own test rig!
    FeatureEnumTest.assertGoodFeatureEnum(FeatureUtilTest.ExampleBaseFeature.class);
    FeatureEnumTest.assertGoodFeatureEnum(FeatureUtilTest.ExampleDerivedFeature.class);
  }

  private static class ConflictingRequirementsExampleDerivedInterfaceTester
      extends ExampleBaseInterfaceTester {}

  public void testTestFeatureEnums() throws Exception {
    // Haha! Let's test our own test rig!
    FeatureEnumTest.assertGoodFeatureEnum(FeatureUtilTest.ExampleBaseFeature.class);
    FeatureEnumTest.assertGoodFeatureEnum(FeatureUtilTest.ExampleDerivedFeature.class);
  }