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The value of the --tests option is a regular expression. Keep it simple. But notice this is a ".*" not simply "*". This is not a command line "*" it is a regular expression "*", which must follow something to be matched.
Warning: if you get the class name wrong, it doesn't complain to you. It just iterates its way through all the potential testable modules, saying "No tests to run for ...". Not very helpful for finding out you had a typographical error in the class name.