@Override
    public void execute(@Nonnull Runnable command) {
        throwRejectedExecutionExceptionIfShutdown();

        command.run();
    }
@Test
    void testExecute() {
        final CompletableFuture<Thread> future = new CompletableFuture<>();
        testTaskSubmissionBeforeShutdown(
                testInstance ->
                        testInstance.execute(() -> future.complete(Thread.currentThread())));

        assertThat(future).isCompletedWithValue(Thread.currentThread());
    }