Description
Describe the bug
I'm using pytest-xdist to run my tests in parallel (mostly a single test parameterized for a vast amount of different test data). Since I wanted to try snapshot-based testing, I've added syrupy to the mix. After initial creation of __snapshots__/mytest.ambr (using the --snapshot-update), it disappears from disk at some point during the test run. Without pytest-xdist (i.e. without using -n auto option) this doesn't happen.
To reproduce
I don't have a clean reproduction, only an observation. My setup is a single test for a bit of processing, parameterized with a couple of hundreds different input files. While the .ambr file appear initially, after about 80% of tests done, the file disappears.
Expected behavior
Snapshot files get updated with correct data without disappearing, even when used with pytest-xdist or pytest-parallel.
Environment:
- OS: Ubuntu 20.04
- Syrupy Version: 1.4.0
- Python Version: 3.8
Additional context
I assume the problem happens because each test execution writes to the file individually and thus a race condition happens. Not sure what can be done about it, maybe buffer the snapshot file somewhere and write it only at the end of the test run? There are surely better ideas. I assume that e.g. the JUnit reporter works correctly with pytest-xdist, maybe check what it does?
Either way, I wanted to bring this to your attention, would be happy if there was a short- to middle-term solution. If not, I'll run the suite without parallelization, it's not that big of a deal at the moment, at least for me :)