assertThat(getDone(immediateFuture("a"))).isEqualTo("a");
  }

  public void testSuccessfulNull() throws ExecutionException {
    assertThat(getDone(immediateVoidFuture())).isEqualTo(null);
  }

  public void testFailed() {
    Exception failureCause = new Exception();
    ExecutionException expected =
        assertThrows(ExecutionException.class, () -> getDone(immediateFailedFuture(failureCause)));