this.pattern = Preconditions.checkNotNull(pattern);
  }

  /*
   * Our implementation works fine with a null `dir`. However, there's nothing in the documentation
   * of the supertype that suggests that implementations are expected to tolerate null. That said, I
   * see calls in Google code that pass a null `dir` to a FilenameFilter.... So let's declare the

  }

  public void testAccept() {
    File dir = new File("foo");
    FilenameFilter filter = new PatternFilenameFilter("a+");
    assertTrue(filter.accept(dir, "a"));
    assertTrue(filter.accept(dir, "aaaa"));
    assertFalse(filter.accept(dir, "b"));

    // Show that dir is ignored
    assertTrue(filter.accept(null, "a"));
  }

  public void testNulls() throws Exception {

    Files.createDirectories(fs.getPath("dir/b/i/j/l"));
    Files.createFile(fs.getPath("dir/a"));
    Files.createFile(fs.getPath("dir/c"));
    Files.createSymbolicLink(fs.getPath("dir/d"), fs.getPath("b/i"));
    Files.createDirectory(fs.getPath("dir/e"));
    Files.createSymbolicLink(fs.getPath("dir/f"), fs.getPath("/dontdelete"));
    Files.createFile(fs.getPath("dir/b/g"));

    File dir1 = newDir("dir-1");
    newFile("dir-1/file-b");
    newFile("dir-1/dir-2");

    assertThat(Iterables.limit(Files.fileTraverser().breadthFirst(rootDir), 3))
        .containsExactly(rootDir, fileA, dir1);
  }

  public void testFileTraverser_multipleDirectoryLayers_traversalReturnsAll() throws Exception {
    File fileA = newFile("file-a");
    File dir1 = newDir("dir-1");

  }

  public void testAccept() {
    File dir = new File("foo");
    FilenameFilter filter = new PatternFilenameFilter("a+");
    assertTrue(filter.accept(dir, "a"));
    assertTrue(filter.accept(dir, "aaaa"));
    assertFalse(filter.accept(dir, "b"));

    // Show that dir is ignored
    assertTrue(filter.accept(null, "a"));
  }

  public void testNulls() throws Exception {

      for (int counter = 0; counter < TEMP_DIR_ATTEMPTS; counter++) {
        File tempDir = new File(baseDir, baseName + counter);
        if (tempDir.mkdir()) {
          return tempDir;
        }
      }
      throw new IllegalStateException(
          "Failed to create directory within "
              + TEMP_DIR_ATTEMPTS
              + " attempts (tried "
              + baseName

  }

  /**
   * Creates a new temp dir for testing. The returned directory and all contents of it will be
   * deleted in the tear-down for this test.
   */
  protected final File createTempDir() throws IOException {
    File tempFile = File.createTempFile("IoTestCase", "");
    if (!tempFile.delete() || !tempFile.mkdir()) {
      throw new IOException("failed to create temp dir");
    }
    filesToDelete.add(tempFile);

    // with/relative/directory is the Class-Path value in the mf file.
    Manifest manifest = manifestClasspath("with/relative/dir");
    assertThat(ClassPath.getClassPathFromManifest(jarFile, manifest))
        .containsExactly(fullpath("base/with/relative/dir"));
  }

  public void testGetClassPathFromManifest_relativeJar() throws IOException {
    File jarFile = new File("base/some.jar");

  /** User's account name. */
  USER_NAME("user.name"),

  /** User's home directory. */
  USER_HOME("user.home"),

  /** User's current working directory. */
  USER_DIR("user.dir");

  private final String key;

  StandardSystemProperty(String key) {
    this.key = key;
  }

  /** Returns the key used to look up this system property. */
  public String key() {

    // with/relative/directory is the Class-Path value in the mf file.
    Manifest manifest = manifestClasspath("with/relative/dir");
    assertThat(ClassPath.getClassPathFromManifest(jarFile, manifest))
        .containsExactly(fullpath("base/with/relative/dir"));
  }

  public void testGetClassPathFromManifest_relativeJar() throws IOException {
    File jarFile = new File("base/some.jar");