ImmutableList.Builder<String> builder = ImmutableList.builder();
    source.forEachLine(builder::add);
    assertExpectedLines(builder.build());
  }

  private void assertExpectedString(String string) {
    assertEquals(expected, string);
  }

  private void assertExpectedLines(List<String> list) {
    assertEquals(expectedLines, list);
  }

      assertNull(source.readFirstLine());
    } else {
      assertEquals(expectedLines.get(0), source.readFirstLine());
    }
  }

  public void testReadLines_toList() throws IOException {
    assertExpectedLines(source.readLines());
  }

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

  public void testLength() throws IOException {