You don’t need to mess with class loaders. In fact it’s a bad habit to get into because class loader resources are not java.io.File objects when they are in a jar archive.
Maven automatically sets the current working directory before running tests, so you can just use:
File resourcesDirectory = new File("src/test/resources");
resourcesDirectory.getAbsolutePath()
will return the correct value if that is what you really need.
I recommend creating a src/test/data
directory if you want your tests to access data via the file system. This makes it clear what you’re doing.