Unit tests to protect against breaking pluggable function changes

[johnbillion]

In [33023] and [33620], the parameters of the pluggable wp_new_user_notification() function were changed, which caused breakage. See #33654.

We can introduce unit tests which protect us against this by using reflection to compare the functions in pluggable.php against an array of expected signatures (well, parameter names and default values at least). That way, if a pluggable function's parameters are changed, the unit tests will fail.

It's not fool-proof (a parameter can be re-purposed without having its name or default value changed), but it gets us a long way.

[johnbillion]

Any of the following changes will cause the tests in 33867.patch​ to fail:

• Renaming a pluggable function parameter.
• Changing, adding, or removing the default value of a pluggable function parameter.
• Deleting a pluggable function, or moving it outside of pluggable.php.
• Adding a new pluggable function.

[adamsilverstein]

add @group pluggable

[adamsilverstein]

This is a great idea John, thanks!.

I tested locally and verified the test fail when i changed a pluggable function parameter signature.

What do you think about adding @group pluggable to the header? I added this to help me run just these tests and notice we already have some tests in this group. Added in 33867.2.patch​.

Replying to johnbillion:

Any of the following changes will cause the tests in 33867.patch​ to fail:

• Renaming a pluggable function parameter.
• Changing, adding, or removing the default value of a pluggable function parameter.
• Deleting a pluggable function, or moving it outside of pluggable.php.
• Adding a new pluggable function.

[boonebgorges]

Good idea, and clever implementation. +1 from me.

[johnbillion]

In 34126:

Implement unit tests which use reflection to test functions in pluggable.php. This means any changes to these functions will need explicit changes to their corresponding tests, which helps prevent unintentional breakage.

Fixes #33867

[johnbillion]

In 34607:

Add function signature tests for the pluggable functions in wp-includes/cache.php.

See #33867

[johnbillion]

In 34608:

Add function signature tests for the pluggable functions in wp-admin/includes/schema.php and wp-admin/includes/upgrade.php.

See #33867

[johnbillion]

In 35145:

Remove wp_cache_reset() from the pluggable functions signature tests, as the function is deprecated and no longer used.

See #31491, #33867

[ocean90]

In 35148:

Improve [35146] to only skip pluggable function signature tests for wp-includes/cache.php when an external object cache is in use.

See #31491, #33867.