Well, I'm surprised to see after double checking that, [despite the docs on data providers only showing examples as instance methods](http://phpunit.de/manual/3.7/en/writing-tests-for-phpunit.html#writing-tests-for-phpunit.data-providers), PHPUnit [handles both cases](https://github.com/sebastianbergmann/phpunit/blob/master/src/Util/Test.php#L369-L373). So I guess it doesn't matter and is even more logical to declare them statically.