Remove dependency to guava testlib

[flo-dup]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem? No

What kind of change does this PR introduce? Library update

What is the current behavior? Junit has been updated to version 5 but guava-testlib is still used and links to version 4

What is the new behavior (if this is a feature change)? No dependcy to Junit 4 remains.

Does this PR introduce a breaking change or deprecate an API? No