@CanIgnoreReturnValue
  public PathSubject containsLines(Iterable<String> lines) throws IOException {
    isRegularFile();

    List<String> expected = ImmutableList.copyOf(lines);
    List<String> actual = Files.readAllLines(this.actual, charset);
    check("lines()").that(actual).isEqualTo(expected);
    return this;
  }
Asserts that the file is a regular file containing the given lines of text. By default, the
bytes are decoded as UTF-8; for a different charset, use {@link #withCharset(Charset)}.
jimfs/src/test/java/com/google/common/jimfs/PathSubject.java