Remove testing code from plugin

[kraftner]

Summary

As noticed in #103 it is not ideal to handle the loading of testing data inside the production plugin code as said in #111.

I've been thinking about several approaches: This PR proposes the one I like the most.

Relevant technical choices:

• No code left in Plugin itself
• Load dev bootstrap with composers autoload/files functionality
• Use normal composer autoloader with PHP 5.3.2+ as xrstf/composer-php52 apparently doesn't support the files autoload functionality, hence this only works with PHP 5.3.2+. But as this is only needed for client-side tests those shouldn't really care about the PHP version in use.
• Adds hooks before WP is initialized by adding a hook to global $wp_filter

Test instructions

This PR can be tested by following these steps:

• Checkout the branch and make sure to composer dumpautoload afterwards so the autoloader is regenerated.

Possibly fixes #111

[moorscode]

Make the code a bit more readable and use Monkey Brains to define the add_action method to reduce mock code.

[moorscode]

We prefer to have a negated condition check and do a return instead of encapsulating this piece of code with the condition indentation.

[moorscode]

Would be less complicated if you can create a variable to hold the file to be loaded.
Defaulting to vendor/autoload.php and making an exception to overwrite with the autoload_52.php version.

After that we only have to use one is_file and require call with that same variable.

[moorscode]

CS: Missing spaces around the else statement.

[moorscode]

I have tried to manually trigger the Monkey Brains setup method, to avoid having to use the ugly global WordPress mocking.

The following code snippet works as expected and removes all problems we have with the current approach.

// Load Monkey Brains WP mock methods.
Brain\Monkey\setUp();

add_action( 'admin_init', 'yoast_acf_analysis_test_data_loader', 11 );

[kraftner]

Oh, this code isn't mocking add_action but actually adds a filter by messing with the globals before the plugin API is ready.

But I just realised that that isn't needed anyway because the autoloader only gets loaded after the Plugin API is ready anyway. So I can further simplify this.

[kraftner]

...and that was there for a reason because of course when running Unit Tests the Plugin API isn't ready. Your alternative approach is nice though. I just wrapped it inside a conditional now because otherwise Brain\Monkey\setUp() is also called during normal execution which needlessly loads Patchwork.

[kraftner]

@moorscode Thanks for your feedback, I have updated the PR. After some messing around I realised that we only really need to load the test data when we're actually in the context of WP with the Plugin API available because in Unit Tests we don't need the test data anyway. See my ramblings for details.
I think this is now clean, simple and ready for merging.

[moorscode]

I agree, have tested this by running the unit tests and confirmed that it works.
Running nightwatch also loads the code as expected.
CR done!
Acceptance done!