Provide full test example

In my opinion providing the full code for the example only adds a few additional lines, but increases the value of the example greatly.

Of course the name for the test should probably be changed as couldn't think of a good one. ping @stof

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3
| Fixed tickets |
I would actually like to have this as a "real" docblock:

```php
/**
 * @dataProvider provideUrls
 */
```