}

  public void testBuildTwice() {
    ThreadFactory unused;
    unused = builder.build(); // this is allowed
    unused = builder.build(); // this is *also* allowed
  }

  public void testBuildMutate() {
    ThreadFactory factory1 = builder.setPriority(1).build();
    assertEquals(1, factory1.newThread(monitoredRunnable).getPriority());

    builder.setPriority(2); // change the state of the builder