There were two sets of tests for `is_serialized()`:
* One in the `functions.php` file, based on the same file name in core.
* One in a separate class in the `functions` directory.
To avoid confusion and make it easier to decide where new tests should go in the future, the existing tests are now combined in the latter location.
Includes:
* Moving `is_serialized()` and `maybe_serialize()` tests into their own classes.
* Using named data providers to make test output more descriptive.
* Combining test cases and removing duplicates.
Follow-up to [278/tests], [279/tests], [328/tests], [32631], [45754], [47452], [49382], [53886], [53889].
See #55652.
git-svn-id: https://develop.svn.wordpress.org/trunk@53890 602fd350-edb4-49c9-b593-d223f7449a82
d1e22dbad8