Tests: all test classes should be either final or abstract

[jrfnl]

Description

Declare all test classes as final.

Classes belonging to the test framework have been exempted at this time.

This may be revisited at a later point in time when addressing issue #25.

Note: by rights, the same should be done for most other classes, but as sniffs are often extended (even though that's not a good idea in most cases), that would be a breaking change, so will have to wait until a later point in time.

Suggested changelog entry

N/A

[jrfnl]

N.B.: PHPCS itself does not contain a sniff to enforce this, though there are various external standards which do have sniffs available. So for now, this will not be enforced via the PHPCS native ruleset and some clean up once in a while for newly introduced test classes may be needed.

[fredden]

N.B.: PHPCS itself does not contain a sniff to enforce this, though there are various external standards which do have sniffs available. So for now, this will not be enforced via the PHPCS native ruleset and some clean up once in a while for newly introduced test classes may be needed.

Would you be open to a pull request which adds an external standard to require-dev in composer.json (and relevant changes to phpcs.xml.dist) to achieve this?

[jrfnl]

@fredden Not at this time, but let's discuss this further in #155.

[jrfnl]

@fredden Note: we could even consider - for the time being - running a few external sniffs via CI only. Adding external standards as dev dependencies will complicate things, so for now, that's not on the table.