There are 2 issues in the `MwApiContentProvider` class in `/content-providers/` which 1 will affect testing the class and the other is just an improvement.
1. Wrapping the call to `file_get_contents()` so it can be stubbed and using MediaWikiServices HttpRequestFactory class to make an HTTP request. The benefit of this is; the class will be easily testable and data can easily be injected (DI) during tests. Also, will avoid the use of suppressing warnings and all that messy stuff :)
2. The use of MediaWiki's JSON Formatter class, `FormatJson::decode()` instead of `json_decode()` which is generally advised to be used; https://doc.wikimedia.org/mediawiki-core/master/php/classFormatJson.html.
This minor refactoring will improve on the over all functionality and efficiency of the code and provides an easy way of testing this class.