Improvement/add unit tests

[Tit-Co]

Summary

• Implement some improvements after fixing the first bug in the "Issues" section of the repository.

Improvements

Unit tests

• Created /unit_tests folder with conftest.py (fixtures) and test_app.py files.
• Added some unit tests in order to test the differents routes from server.py.
• Three tests confirmed several bugs listed in the "Issues" section of the repository.

What has been tested ?

Succeed tests

• Index page status code 200.
• Index page returns welcome content.
• Index page authentication status code 200.
• Index page authentication succeed and returns summary content.
• Index page authentication fails with unknown mail (status code 404).
• Summary page logout status code ok (status code 302).
• Summary page logout succeed and redirects to welcome page.
• Booking page status code 200.
• Booking page and returns festival page content.
• Purchasing places page status code 200.

Failed tests

• Purchasing places succeed and return summary page content (one assertion failed, confirms one bug in Issues).
• Purchasing places failed with not enough points (status code should be 403, confirms one bug in Issues).
• Purchasing places failed with more than 12 places (status code should be 403, confirms one bug in Issues).