I do feel ... awkward adding a function call here on such a commonly used method. Alternatively I could revert adding this method and instead just change the test case to create arbitrary class names for the purpose of testing the various permutations of the classname function, [this is the case](https://github.com/cakephp/cakephp/pull/2432/files#diff-a1639fedae0cc23b90f9634c43233678R84) that currently isn't possible and should be.

Would it be way out to consider treating `Cake` as a plugin?

    public $components = [
        'Cake.Auth'
    ]

That way we could eliminate the class_exists calls completely.