Change experiment initialization method from register() to init()

[juanmaguitar]

What?

Refactors the experiment lifecycle method from register() to init() across the entire codebase to better reflect its purpose of initializing experiments.

Closes #145

Why?

The term "register" was misleading as it suggested the experiments were being registered into a system, when in reality this method is called after registration to initialize the experiment's hooks and functionality. The method init() more accurately describes what the method does - it initializes the experiment by setting up WordPress hooks, filters, and actions when the experiment is enabled and loaded.

This improves code clarity and aligns the method naming with its actual behavior in the experiment lifecycle:

1. Experiments are registered to the registry via Experiment_Registry::register()
2. Experiments are initialized via Experiment::init() when they're loaded

How?

• Updated the Experiment interface to declare init() instead of register()
• Updated the Abstract_Experiment abstract class to declare abstract public function init()
• Updated all concrete experiment implementations:
  • Example_Experiment
  • Excerpt_Generation
  • Image_Generation
  • Title_Generation
• Updated Experiment_Loader::initialize_experiments() to call init()
• Updated all test mock classes and test assertions
• Updated developer documentation and inline comments

Testing Instructions

1. Enable the AI Experiments plugin
2. Go to Settings → AI Experiments
3. Enable one or more experiments
4. Verify the experiments load correctly and their functionality works as expected
5. Check that no PHP errors or warnings appear in the debug log
6. Run the full test suite: npm run test:php
7. Verify all tests pass

Testing Instructions for Keyboard

Not applicable - this is an internal refactoring with no UI changes.

[github-actions]

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Co-authored-by: juanmaguitar <juanmaguitar@git.wordpress.org>
Co-authored-by: JasonTheAdams <jason_the_adams@git.wordpress.org>
Co-authored-by: justlevine <justlevine@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.89%. Comparing base (6478545) to head (50d96f7).
⚠️ Report is 7 commits behind head on develop.

Files with missing lines	Patch %	Lines
...eriments/Excerpt_Generation/Excerpt_Generation.php	0.00%	1 Missing ⚠️
.../Experiments/Title_Generation/Title_Generation.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #159   +/-   ##
==========================================
  Coverage      46.89%   46.89%           
  Complexity       208      208           
==========================================
  Files             19       19           
  Lines           1271     1271           
==========================================
  Hits             596      596           
  Misses           675      675           

Flag	Coverage Δ
unit	46.89% <60.00%> (ø)

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[juanmaguitar]

"Plugin Check" workflow is failing due to an issue reported at #160

[jeffpaul]

#160 has been merged in, so hopefully an update from develop will get the plugin check passing @juanmaguitar

[JasonTheAdams]

Minor wording suggestion, but otherwise looks good!

[JasonTheAdams]

Suggested change

	// Initialize your hooks here
	// Initializes your experiment. Use this to set up your needed hooks.

[justlevine]

I very much disagree with the proposed change, and the premise that . The method init() more accurately describes what the method does

Registration != instantiation, and add_action() / add_filter() are very much registration methods and not instantiation. It's only later in the lifecycle when those hooks are actually called that the bulk of the time we want any initialization to happen, and very rarely when our hook callbacks are registered onto the WordPress lifecycle.

Moreover the conflation between the two leads to unnecessary headaches around lifecycle and testing, and we shouldnt be registering hooks in an ::init() any more than we should be doing it in a __contruct() - and for the exact same reasons.

---

If we want to add an Initializable interface to pair with a Registrable interface as a way to allow for experiments to have an generic instantiation (instead of just letting it happen inside the hooks), I would be much more amenable. But that seems even more unnecessary at this stage than this proposed rename. In the super rare situation that an Experiment needs to "::init()" functionality when our registry $experiment->register() - and not when WordPress actually loads / runs the experiment code - it can be an implementation detail of the experiment.

Alternatively, if you think ::register() is confusing because it's the function that we call when we register it (? not sure if I understood this argument correctly... like wouldn't that be the exact type of function for a registry to call???), then as a middle ground I'd suggest ::register_hooks(). That IMO might be unnecessary bikeshedding, but at least there's no future code quality implications...

[justlevine]

Marking as Request changes to ensure a conversation is had #159 (comment) - obvs is the majority disagree I'm good with being overruled 🙇

[juanmaguitar]

@justlevine Appreciate the feedback — I agree with your reasoning.

I’m in favor of using register_hooks instead of init to better separate the two types of "register" in the experiment lifecycle following WordPress standards:

• $registry->register_experiment() — adds the experiment to the internal registry.
• $experiment->register_hooks() — attaches the WordPress hooks and effectively “starts” the experiment.

I’d love to hear more thoughts before moving ahead with any changes on this matter.