MoreFiles.touch(temp);
    assertThat(Files.getLastModifiedTime(temp).toMillis()).isNotEqualTo(0);
  }

  public void testCreateParentDirectories_root() throws IOException {
    // We use a fake filesystem to sidestep flaky problems with Windows (b/136041958).
    try (FileSystem fs = Jimfs.newFileSystem(Configuration.unix())) {
      Path root = fs.getRootDirectories().iterator().next();

    Runnable runMe =
        new Runnable() {
          @Override
          public void run() {
            numCalls.incrementAndGet();
            throw new RuntimeException("FAKE EXCEPTION!");
          }
        };

    e.execute(runMe);
    e.execute(runMe);
    fakePool.runAll();

    assertEquals(2, numCalls.get());
  }

    Runnable runMe =
        new Runnable() {
          @Override
          public void run() {
            numCalls.incrementAndGet();
            throw new RuntimeException("FAKE EXCEPTION!");
          }
        };

    e.execute(runMe);
    e.execute(runMe);
    fakePool.runAll();

    assertEquals(2, numCalls.get());
  }

            int behavior = random.nextInt(4);
            if (behavior == 0) { // throw an exception
              exceptionCount.incrementAndGet();
              throw new RuntimeException("fake exception for test");
            } else if (behavior == 1) { // return null
              computeNullCount.incrementAndGet();
              return null;
            } else if (behavior == 2) { // slight delay before returning

     * Given that we declare this method as accepting and returning non-nullable values (because we
     * implement Function<A, B>, as discussed in a class-level comment), it would make some sense to
     * perform runtime null checks on the input and output. (That would also make NullPointerTester
     * happy!) However, since we didn't do that for many years, we're not about to start now.

      list.add(i);
    }

    Ordering<Object> arbitrary =
        new ArbitraryOrdering() {
          @Override
          int identityHashCode(Object object) {
            return ((Integer) object) % 5; // fake tons of collisions!
          }
        };

    // Don't let the elements be in such a predictable order
    list = shuffledCopy(list, new Random(1));

    Collections.sort(list, arbitrary);

      list.add(i);
    }

    Ordering<Object> arbitrary =
        new ArbitraryOrdering() {
          @Override
          int identityHashCode(Object object) {
            return ((Integer) object) % 5; // fake tons of collisions!
          }
        };

    // Don't let the elements be in such a predictable order
    list = shuffledCopy(list, new Random(1));

    Collections.sort(list, arbitrary);

     * Given that we declare this method as accepting and returning non-nullable values (because we
     * implement Function<A, B>, as discussed in a class-level comment), it would make some sense to
     * perform runtime null checks on the input and output. (That would also make NullPointerTester
     * happy!) However, since we didn't do that for many years, we're not about to start now.

   *     class under test.
   */
  protected abstract Map<K, V> makeEmptyMap() throws UnsupportedOperationException;

  /**
   * Creates a new, non-empty instance of the class under test.
   *
   * @return a new, non-empty map instance.
   * @throws UnsupportedOperationException if it's not possible to make a non-empty instance of the
   *     class under test.

      // we allow one second worth of work to go in a burst (i.e. take less than a second)
      assertTrue(burst <= 1000);
      long afterBurst = measureTotalTimeMillis(limiter, oneSecWorthOfWork, new Random());
      // but work beyond that must take at least one second
      assertTrue(afterBurst >= 1000);
    }
  }

  /**