assertThat(MoreFiles.equal(fooPath, barPath)).isFalse();
      assertThat(MoreFiles.equal(fooPath, fooPath)).isTrue();
      assertThat(MoreFiles.asByteSource(fooPath).contentEquals(MoreFiles.asByteSource(fooPath)))
          .isTrue();

      Path fooCopy = Files.copy(fooPath, fs.getPath("fooCopy"));
      assertThat(Files.isSameFile(fooPath, fooCopy)).isFalse();

    long len1 = source1.sizeIfKnown().or(0L);
    long len2 = source2.sizeIfKnown().or(0L);
    if (len1 != 0 && len2 != 0 && len1 != len2) {
      return false;
    }
    return source1.contentEquals(source2);
  }

  /**
   * Like the unix command of the same name, creates an empty file or updates the last modified
   * timestamp of the existing file at the given path to the current system time.
   */

    long len1 = source1.sizeIfKnown().or(0L);
    long len2 = source2.sizeIfKnown().or(0L);
    if (len1 != 0 && len2 != 0 && len1 != len2) {
      return false;
    }
    return source1.contentEquals(source2);
  }

  /**
   * Like the unix command of the same name, creates an empty file or updates the last modified
   * timestamp of the existing file at the given path to the current system time.
   */