assertThat(lowerCase).isNotSameInstanceAs(base16());
    assertThat(lowerCase).isSameInstanceAs(base16().lowerCase());
    testEncodingWithCasing(lowerCase, "foobar", "666f6f626172");
  }

  public void testBase16IgnoreCase() {
    BaseEncoding ignoreCase = base16().ignoreCase();
    assertThat(ignoreCase).isNotSameInstanceAs(base16());

    assertThat(lowerCase).isNotSameInstanceAs(base16());
    assertThat(lowerCase).isSameInstanceAs(base16().lowerCase());
    testEncodingWithCasing(lowerCase, "foobar", "666f6f626172");
  }

  public void testBase16IgnoreCase() {
    BaseEncoding ignoreCase = base16().ignoreCase();
    assertThat(ignoreCase).isNotSameInstanceAs(base16());

  }

  public void testImpliedFeatures_returnsNewSetInstance() {
    Set<Feature<?>> features = newHashSet(IMPLIES_FOO);
    assertThat(impliedFeatures(features)).isNotSameInstanceAs(features);
  }

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

    assertThat(Bytes.concat(EMPTY)).isEqualTo(EMPTY);
    assertThat(Bytes.concat(EMPTY, EMPTY, EMPTY)).isEqualTo(EMPTY);
    assertThat(Bytes.concat(ARRAY1)).isEqualTo(ARRAY1);
    assertThat(Bytes.concat(ARRAY1)).isNotSameInstanceAs(ARRAY1);
    assertThat(Bytes.concat(EMPTY, ARRAY1, EMPTY)).isEqualTo(ARRAY1);
    assertThat(Bytes.concat(ARRAY1, ARRAY1, ARRAY1))
        .isEqualTo(new byte[] {(byte) 1, (byte) 1, (byte) 1});

    assertDoesntActuallyTrim(iia2);
  }

  private static void assertActuallyTrims(ImmutableLongArray iia) {
    ImmutableLongArray trimmed = iia.trimmed();
    assertThat(trimmed).isNotSameInstanceAs(iia);

    // Yes, this is apparently how you check array equality in Truth
    assertThat(trimmed.toArray()).isEqualTo(iia.toArray());
  }

    assertDoesntActuallyTrim(iia2);
  }

  private static void assertActuallyTrims(ImmutableDoubleArray iia) {
    ImmutableDoubleArray trimmed = iia.trimmed();
    assertThat(trimmed).isNotSameInstanceAs(iia);

    // Yes, this is apparently how you check array equality in Truth
    assertThat(trimmed.toArray()).isEqualTo(iia.toArray());
  }

    assertThat(Chars.concat(EMPTY)).isEqualTo(EMPTY);
    assertThat(Chars.concat(EMPTY, EMPTY, EMPTY)).isEqualTo(EMPTY);
    assertThat(Chars.concat(ARRAY1)).isEqualTo(ARRAY1);
    assertThat(Chars.concat(ARRAY1)).isNotSameInstanceAs(ARRAY1);
    assertThat(Chars.concat(EMPTY, ARRAY1, EMPTY)).isEqualTo(ARRAY1);
    assertThat(Chars.concat(ARRAY1, ARRAY1, ARRAY1))
        .isEqualTo(new char[] {(char) 1, (char) 1, (char) 1});

    assertThat(Doubles.concat(EMPTY)).isEqualTo(EMPTY);
    assertThat(Doubles.concat(EMPTY, EMPTY, EMPTY)).isEqualTo(EMPTY);
    assertThat(Doubles.concat(ARRAY1)).isEqualTo(ARRAY1);
    assertThat(Doubles.concat(ARRAY1)).isNotSameInstanceAs(ARRAY1);
    assertThat(Doubles.concat(EMPTY, ARRAY1, EMPTY)).isEqualTo(ARRAY1);
    assertThat(Doubles.concat(ARRAY1, ARRAY1, ARRAY1)).isEqualTo(new double[] {1.0, 1.0, 1.0});

    assertThat(Ints.concat(EMPTY)).isEqualTo(EMPTY);
    assertThat(Ints.concat(EMPTY, EMPTY, EMPTY)).isEqualTo(EMPTY);
    assertThat(Ints.concat(ARRAY1)).isEqualTo(ARRAY1);
    assertThat(Ints.concat(ARRAY1)).isNotSameInstanceAs(ARRAY1);
    assertThat(Ints.concat(EMPTY, ARRAY1, EMPTY)).isEqualTo(ARRAY1);
    assertThat(Ints.concat(ARRAY1, ARRAY1, ARRAY1))
        .isEqualTo(new int[] {(int) 1, (int) 1, (int) 1});

    assertDoesntActuallyTrim(iia2);
  }

  private static void assertActuallyTrims(ImmutableIntArray iia) {
    ImmutableIntArray trimmed = iia.trimmed();
    assertThat(trimmed).isNotSameInstanceAs(iia);

    // Yes, this is apparently how you check array equality in Truth
    assertThat(trimmed.toArray()).isEqualTo(iia.toArray());
  }