What is .phpunit.result.cache
This file helps PHPUnit remember which tests previously failed, which can speed up your testing flow if you only re-run failed tests during development. This is useful for test-driven workflows in which you have configured tests to run automatically, such as on file save, and the same collection of tests is being run repeatedly.
It is also a good idea to add the cache file .phpunit.result.cache toyour .gitignore so that it does not end up being committed to yourrepository.
If you would prefer not to generate the file then you can run phpunit with the --do-not-cache-result option, as pointed out by @Slack Undertow in the comments. This might be desired when running tests as part of a build pipeline, for example. Or, as @codekandis pointed out, the same option is available as the cacheResult attribute in phpunit.xml.
You can also change this file location by editing phpunit.xml:
<phpunit ... cacheResultFile="../.temp/fs_cache/.phpunit.result.cache">Or completely disable it by
<phpunit ... cacheResult ="false">