Catch deprecations as part of test suite

[MasterOdin]

From #83 (comment), this PR enables failing tests if they throw deprecations. This required updating the CI pipeline as the shivammathur/setup-php@v2 does error_reporting=E_ALL | ~E_STRICT | ~E_DEPRECATION by default for PHP 8+ (ref: shivammathur/setup-php#450) as well as updating configuration for phpunit to convert deprecations into errors.

No existing tests fail from this change.

[willpower232]

I'm confused, shouldn't this have revealed a failure based on the other PR? Or is there a test missing?

In an ideal world, this PR would fail on tests and #83 would then make the tests pass but they haven't failed yet...

Or am I misunderstanding completely?

[MasterOdin]

My view would be in an ideal world a PR with a bugfix or feature includes a test for that fix or feature. If the merged PR needs to be reverted for whatever reason, so to could be the test. This also keeps the default branch consistently "green" as a primary goal.

This PR is just making it so that that test (and future tests) would probably validate that a deprecation warning is not being thrown.

I'm confused, shouldn't this have revealed a failure based on the other PR? Or is there a test missing?

There are currently no tests that covers setting the $issuer to null, and so catching the deprecations would not cause any "new" failures. As part of #83, a test should be added for that particular case though.

[willpower232]

Test added in 4f1543f and deprecation finally detected with this PR merged