The setup for unit testing in Github in the "Install dependencies" log reports 11 members as "does not comply with with psr-4 autoloading standard." In each case, it is because the test namespace does not match the directory; in most cases, it was caused by the member being moved from one directory to another without changing the namespace declaration. No harm results from these problems, but there's also no reason to not correct them.
* Rename Two Test Files
When I run unit tests only for Reader/Xlsx, phpunit is issuing a deprecation message because the names of 2 files have an extra dot in them and thus don't match the class name in the file. I do not see these warnings when I run the entire test suite.
* Remove Phpstan Annotations
It was a bit difficult to handle a cast from mixed to string.
* Fix Same Phpstan Problem in One Other Test
This is the only other test case that tries to cast mixed to string.