[TIP] setup pytest fixtures in parallel

Bruno Oliveira nicoddemus at gmail.com
Fri Nov 24 01:19:16 PST 2017

Hi Wouter,

As Ronny said, it is currently impossible for pytest to do this for you
automatically, but I believe it is possible to accomplish that with some
work yourself:

1. Create a session-scoped fixture which returns a
2. Modify each fixture which you want to run in parallel to receive the
executor, and instead of doing its work directly into the body of the
fixture, move that to a function and post the function to the executor.
Return the Future object.
3. Each function which uses one of the fixtures in parallel will have to be
modified to deal with a Future object.

Hope that helps,

On Fri, Nov 24, 2017 at 5:32 AM RonnyPfannschmidt <
opensource at ronnypfannschmidt.de> wrote:

> Hi Wouter,
> currently there is no way to do fixture setup in parallel and also no
> underlying structure to implement concurrent and/or parallel fixture
> creation.
> enabling something like it is no easy feat and requires a major rework of
> the internals of the pytest fixture system.
> -- Ronny
> Am 24.11.2017 um 08:02 schrieb Wouter Overmeire:
> Hi,
> Is there a way in pytest (or a plugin) to setup test fixtures in parallel?
> Not running the tests in // but only setup the fixtures in //.
> Suppose I have a number of tests and each have a different number of
> fixtures.
> The fixtures take long to setup, given they are independent of each other
> and not cpu limited, setup could be done in //.
> I prefer not to stuff all fixtures in one major fixture and control from
> this one how to build.
> Not all tests use the same fixtures, and fixtures come and go. Ideally I`m
> looking for a way to add additional decorator (or arg on existing fixture
> pytest decorator) on a fixture indicating it can be setup in //.
> I`m familiar with the concept of scope on fixtures, but even for session
> scoped fixtures I would like to setup them in //.
> Probably not so trivial given fixtures can be hierarchical.
> The hook pytest_fixture_setup looks the way to go, I`m wondering how to
> run rest of the fixture setup chain in a thread and return the fixture when
> done, This feels like breaking the api model behind hooks, given return
> value of hook determines to stop the chain. Not modify rest of the call
> chain.
> Wouter
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