assertExpectedLines(source.readLines());
  }

  public void testIsEmpty() throws IOException {
    assertEquals(expected.isEmpty(), source.isEmpty());
  }

  public void testLength() throws IOException {
    assertEquals(expected.length(), source.length());
  }

  public void testLengthIfKnown() throws IOException {
    Optional<Long> lengthIfKnown = source.lengthIfKnown();

    }

    abstract void doIt(ImmutableLongArray.Builder builder, AtomicLong counter);
  }

  private static final Random random = new Random(42);

  public void testLength() {
    assertThat(ImmutableLongArray.of().length()).isEqualTo(0);
    assertThat(ImmutableLongArray.of(0).length()).isEqualTo(1);
    assertThat(ImmutableLongArray.of(0, 1, 3).length()).isEqualTo(3);