How do I test concurrency for an API?

💬 Question and Help

I am developing a booking app and I want to use the fast-check library to simulate race conditions in my API. Basically, I want to simulate the use case where many users would call the same API to book the same table at the same time :

Suppose this is my API : POST /book with a request body like :

{
   "table": 1,
   "time": "20:00"
}

My koa API looks something like this:

router
    .post('/book', (ctx) => {
        const { table, time } = ctx.request.body;
        const { isBooked } = await checkIfAvailable(table,time).body; // calls MongoDB
        if(!isBooked){
			ctx.body = {
				table,
				time,
				booked: true
			};	
        } else {
			ctx.throw("This table is already booked", 404)
		}
        
    })

My test looks like this :

mockedCheckIfAvailable.mockImplementation(
	s.scheduleFunction(async (table,time) => {
		return  booking;
	}),
);

const  res  =  await  request
	.post('/book')
	.set('Content-Type', 'application/json')
	.set('Accept', 'application/json')
	.send(booking);
expect(res).toBe(true);

I read the Race Conditions docs but I can’t get around how to apply it.

[dubzzz]

Now that I have a clearer idea of what caused the issue, I will certainly add another wait* onto the instance of scheduler. Something like: waitFor that would be able to wait for a promise and unlock potential dependencies it can rely on as they appear. In your case, it would be use to wrap the request.

[dubzzz]

You probably want to try with:

    it('works', async () => {
+++        await fc.assert(
---        fc.assert(