Implement __serialize() on DefaultTestResultCache

[derrabus]

The Serializable interface is being phased out as described in https://wiki.php.net/rfc/phase_out_serializable

The consequence is that PHP 8.1 will trigger a deprecation notice if a class implements Serializable unless it also implements the magic methods __serialize() and __unserialize(). Those have been introduced with PHP 7.4 and are meant to replace the old Serializable mechanism.

PHPUnit's DefaultTestResultCache is affected by this change. This PR proposes to implement __serialize() and __unserialize() to avoid the deprecation.

Because this changes the output of the serialization slightly, I had to adjust a couple of tests.

[codecov]

Codecov Report

Merging #4662 (d71643f) into 8.5 (2c47a3e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##                8.5    #4662   +/-   ##
=========================================
  Coverage     84.21%   84.21%           
- Complexity     3981     3983    +2     
=========================================
  Files           154      154           
  Lines         10185    10187    +2     
=========================================
+ Hits           8577     8579    +2     
  Misses         1608     1608           

Impacted Files	Coverage Δ	Complexity Δ
src/Runner/DefaultTestResultCache.php	93.75% <100.00%> (+0.20%)	31.00 <7.00> (+2.00)

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[sebastianbergmann]

Thank you for working on this, Alexander.

However, it may not be as simple as "just" updating the tests. Is the new code able to load from a cache file created by the old code? It is is: great! If it's not, we need to adapt the loader to not crash when loading a file it does not understand and treat that situation as a cache miss.

[derrabus]

Is the new code able to load from a cache file created by the old code?

It should be. There is a test in this PR that performs an unserialize() with the old format.

[sebastianbergmann]

It should be. There is a test in this PR that performs an unserialize() with the old format.

Thank you for pointing that out, I did not have time yet to (closely) look at the proposed changes.

[derrabus]

However, it does not work the other way round: PHP 7.3 won't be able to unserialize the format generated by PHP 7.4.

[sebastianbergmann]

Good to know, thanks. Only goes to show that using serialize() was not a great choice to begin with.

[sebastianbergmann]

Thank you for your contribution. I appreciate the time you invested in preparing this pull request. However, I have decided not to merge it. Instead, I have changed the implementation of DefaultTestResultCache to not use serialize() / unserialize() at all.

[derrabus]

No worries. Your way is certainly the better solution in the long run!