testDir = createTempDir();
    }

    return testDir;
  }

  /** Returns the file with the given name under the testdata directory. */
  protected final @Nullable File getTestFile(String name) throws IOException {
    File file = new File(getTestDir(), name);
    if (!file.exists()) {
      URL resourceUrl = IoTestCase.class.getResource("testdata/" + name);
      if (resourceUrl == null) {