List<String> temp = new ArrayList<>();
    for (Feature<?> feature : features) {
      Object featureAsObject = feature; // to work around bogus JDK warning
      if (featureAsObject instanceof Enum) {
        Enum<?> f = (Enum<?>) featureAsObject;
        temp.add(f.getDeclaringClass().getSimpleName() + "." + feature);
      } else {
        temp.add(feature.toString());
      }
    }

      assertThrows(IllegalStateException.class, Files::createTempDir);
      return;
    }
    File temp = Files.createTempDir();
    try {
      assertThat(temp.exists()).isTrue();
      assertThat(temp.isDirectory()).isTrue();
      assertThat(temp.listFiles()).isEmpty();
      File child = new File(temp, "child");
      assertThat(child.createNewFile()).isTrue();
      assertThat(child.delete()).isTrue();

      return File.createTempFile(
          /* prefix= */ prefix,
          /* suffix= */ null,
          /* directory= */ null /* defaults to java.io.tmpdir */);
    }

    /** Maximum loop count when creating temp directories. */
    private static final int TEMP_DIR_ATTEMPTS = 10000;
  }

  private static final class ThrowingCreator extends TempFileCreator {
    private static final String MESSAGE =