rb.CloseWithError(errors.New("test error"))
		<-done
	}
	testCancel(func() {
		rb.Write([]byte{sz + 5: 1})
	})
	testCancel(func() {
		rb.Write(make([]byte, sz))
		rb.WriteByte(0)
	})
	testCancel(func() {
		rb.Read([]byte{10: 1})
	})
	testCancel(func() {
		rb.ReadByte()
	})
	testCancel(func() {
		rb.Write(make([]byte, sz))
		rb.Flush()
	})
}

    Exception e = new IllegalArgumentException("foo not found");
    MockCallback callback = new MockCallback(e);
    addCallback(f, callback, directExecutor());
    f.setException(e);
  }

  public void testCancel() {
    SettableFuture<String> f = SettableFuture.create();
    FutureCallback<String> callback =
        new FutureCallback<String>() {
          private final Object monitor = new Object();

    assertFalse(future.isDone());
    assertTrue(future.setException(new Exception("failure")));
    tester.testFailedFuture("failure");
  }

  public void testCancel() throws Exception {
    assertTrue(future.cancel(true));
    tester.testCancelledFuture();
  }

  /** Tests the initial state of the future. */
  public void testCreate() throws Exception {