Increasing accountability through testing and reviews

[CSchoel]

The project might benefit from policies that increase accountability for code changes.
This might include a policy that tests have to be written by someone other than the person who has written the code that is being tested, or that each pull request to the main branch needs to be reviewed by a different person (including myself, if required).

Note: This issue is still work in progress, as it is not designated for the current sprint.