How to use pytest with a legacy in-house test framework

[danieljfarrell]

I use pytest for all my new projects, but I'm working with a large python 3 project that implemented its own test framework; it does not inherit from unittest, it's pure custom python. It follows familiar idioms like setup/teardown, test are class based with assert methods e.g. self.assert_true etc.

I'd like to use pytest as a test runner for the legacy tests and start to write new tests using pytest.

How can I run my old tests with pytest? Is there any documentation about this use case? Or has someone done something similar before?

[arthuRHD]

Hi @danieljfarrell,

It depends whether or not your "custom" test framework supports external runners. But, you might want to migrate your entire test suites in pytest. Here's why:

1. Less maintainance due to complying to pytest guidelines
2. What if you find a working solution with the actual version of pytest but the next one has breaking changes ?
3. Based on what you describe, it might not be that difficult for pytest to work with your test architecture.

[RonnyPfannschmidt]

that strongl depends on the test framework,

if your setup/tearown is in line enough with what pytest expects, it may be possible to just run things (with the caveat of maybe needing to enforce collection of things that have a init)

else you pretty much have to implement own collection and own test item classes (just like the builtin unittest plugin does)

[nicoddemus]

Indeed the builtin unittest plugin would be great place to start.

Also searching for framework in https://docs.pytest.org/en/stable/reference/plugin_list.html might yield plugins which integrate with external frameworks.