[Feature request] Add response delay option

[theoutsider24]

I'd like the option to introduce an artificial delay before returning a response to simulate services which are slow

This is particularly useful in testing asynchronous operations to control responses coming out of order

[markstory]

I have a few questions on how this would work:

1. Wouldn't adding delays slow down tests as you'll have to block on timers completing?
2. How would you indicate to responses that some mocks should have delays applied?

[theoutsider24]

Hey @markstory

Yes it would slow the tests, the use case here is related to asynchronous requests (particularly using requests-futures) where I want to demonstrate a) that if the responses come out of order it's fine and b) that if two async responses both have a delay, the runtime is less than the sum of the delays

a is the kind of thing I may have in my unit test suite, with very small delays (eg. 20-50ms) - just enough to make responses come in out of order b would more likely be for manual testing and PoCs Another use case could be forcing one request to hang while another succeeds/fails with a short delay to demonstrate that the hanging request gets cancelled

Maybe something like this

 responses.add(
        responses.GET,
        "http://twitter.com/api/1/foobar",
        json={"error": "not found"},
        status=404,
        latency=1000 # add 1s of latency
    )

[markstory]

A latency parameter could work well. If the host application isn't using asyncio, I guess we would have to block the main thread for the duration of latency?

[beliaev-maksim]

@markstory if we consider that the delay is artificially added, then it should not play role where it is added in responses

Will in such case matcher work as well?

[markstory]

Yeah, a matcher could be used to add the latency as well. That would save us having to expand the API of responses.add which is nice.

[beliaev-maksim]

@theoutsider24 please try the approach with matcher. We are here to support if you will need help. However, should be pretty straightforward

[beliaev-maksim]

@theoutsider24 were you able to achieve it with matcher?