Test projects usually have a single target framework, while the implementation supports multiple

[stijnmoreels]

Describe the bug
We currently only test out the most recent framework during unit/integration tests. For the unit tests, this is because the Codecov code coverage does not handle well multiple frameworks, and for the integration tests this means double run time.

To Reproduce
Steps to reproduce the behavior:

• Run the CI pipeline.
• Look at how only a single framework is used in the project.

Expected behavior
We could investigate in adding additional arguments to the Codecov command so that we use multiple frameworks for testing, but a single framework for code coverage.

We could investigate in whether it would be workable to run the integration tests in serial with multiple frameworks, or maybe some of them could be run in parallel.