unit test shall be executed automatically on build server

[dhebbeker]

See WIP.

Acceptance criteria:

• all defined unit tests shall be automatically executed for every push to the build server (see if we can use a pattern - or similar - to execute all (future) tests; that is: do not hard-code the names of the tests into a script)
• failing unit tests shall prevent pull requests to be merged

Depends on:

• setup basic infrastructure to run unit tests #51