Incremental test-suite filtering/retrieval #6420
Description
running phpunit --list-tests on phpstan-src@07700d8 runs 7 seconds without any output.
after 7 seconds all the output gets produced and dumbed to the console.
before everything is just black and no progress is reflected to the end user.
phpstan-src has so many tests and the data-providers are doing a considerable amount of work, which means building a list of all tests is getting slow.
I think it would be helpful when the test-suite filtering/retrieval could be build in a streaming way, so output can be shown to the user while more work is done meanwhile (so in a streaming fashing. the enduser would see a more responsive terminal).
I think this would also be useful for paratest, as it currrently needs to wait for the whole test list beeing available before it proceeds in starting workers and runs tests in parallel - see paratestphp/paratest#1049
(although paratest is currently not using the CLI command, but uses the PHP classes from PHPUnit directly)