Broken/deprecated/old JUnit dependencies in pom.xml

The recent commit where JUnit 5 was introduced seems to have broken something. Apparently, the version number for the junit-platform-runner dependency (version 5.0.0-M4) does not exist.

Also, the latest stable version of junit-jupiter-engine is 5.4.2, but the pom.xml declares a version number 5.0.0-M4 also for this dependency.

Besides, I'm getting a warning when trying to run tests:

The junit-platform-surefire-provider has been deprecated and is scheduled to be removed in JUnit Platform 1.4. Please use the built-in support in Maven Surefire >= 2.22.0 instead.

I'm not sure what this means, but I assume it has something to do with the dependencies configured for the surefire plugin, which were not there before.

Besides, I think the appropriate scope for the junit-jupiter-engine dependency is test (currently, it is not set, so it defaults to compile).