docs: update FAQ

docs/developer_guide.md

@@ -101,3 +101,10 @@ To add a new social network to RenderCV, go to the `rendercv/data_models.py` fil
 2. If necessary, implement its username validation in the `SocialNetwork.check_username` method.
 3. Implement its URL generation using the `SocialNetwork.url` method. If the URL can be generated by appending the username to a hostname, only update `url_dictionary`.
 4. Finally, include the $\LaTeX$ icon of the social network to the `icon_dictionary` in the `CurriculumVitae.connections` method. RenderCV uses the [`fontawesome5`](https://ctan.org/pkg/fontawesome5?lang=en) package. The available icons can be seen [here](https://fosszone.csd.auth.gr/CTAN/fonts/fontawesome5/doc/fontawesome5.pdf).
+
+Then, the tests should be implemented for the new social network with the following steps:
+
+1. Go to `tests/test_data_models.py` and update `test_social_network_url` accordingly.
+2. Go to `tests/conftest.py` and add the new social network to `rendercv_filled_curriculum_vitae_data_model`.
+3. Set `update_testdata` to `True` in `conftest.py` and run the tests to update the `testdata` folder.
+4. Review the updated `testdata` folder manually to ensure everything works as expected. Then, set `update_testdata` to `False` and push the changes.