Add snapshot tests

[janivo]

Feature Request

To prevent regression e.g. when updating the MDC libraries, we should have a way to see if anything (e.g. the structure of a component) changed unintentionally.

Description of the proposed solution

Add snapshots tests.

Description of the considered alternatives

An alternative is visual regression testing (a.k.a. screenshot tests). As #683 showed, these seem to be really flaky in our current setup and therefore are not suited for us at the moment.

Additional context

Snapshot testing is already partially implemented by #698 but there is still a problem with components that generate a unique ID to function properly. These ids changes with every render and therefore differ every test run.