Make testing less verbose

[CrochetFeve0251]

Is your feature request related to a problem? Please describe.
Today testing is really verbose, which ends up taking too much time and living a lot of room for mistakes.

Describe the solution you'd like
The goal of that issue is to try to find solutions to make testing easier and more efficient.

For the moment, there are the potential solutions identified:

• Use phpunit-wp-hooks to make filter mocking easier.
• Improve phpunit-wp-hooks to also reset global variables, options and transients.
• Use generators to generate test data which automatically resets the local state on each test.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.