tests: adjust 'extra' tests API to better design from core3

Do not force inheritance of ExtraTestMixin and QubesTestCase. Instead
provide 'qubes.tests.extra.ExtraTestCase' for external tests. This makes
the API less "magic", easier to understand and apply static analysis
tools on it.

QubesOS/qubes-issues#1800

tests/__init__.py

@@ -175,7 +175,7 @@ class QubesTestCase(unittest.TestCase):
 
     def __str__(self):
         return '{}/{}/{}'.format(
-            '.'.join(self.__class__.__module__.split('.')[2:]),
+            self.__class__.__module__,
             self.__class__.__name__,
             self._testMethodName)
 

tests/extra.py

@@ -27,12 +27,12 @@ import qubes.tests
 import qubes.qubes
 
 
-class ExtraTestMixin(qubes.tests.SystemTestsMixin):
+class ExtraTestCase(qubes.tests.SystemTestsMixin, qubes.tests.QubesTestCase):
 
     template = None
 
     def setUp(self):
-        super(ExtraTestMixin, self).setUp()
+        super(ExtraTestCase, self).setUp()
         self.qc.unlock_db()
 
     def create_vms(self, names):
@@ -74,13 +74,7 @@ class ExtraTestMixin(qubes.tests.SystemTestsMixin):
 def load_tests(loader, tests, pattern):
     for entry in pkg_resources.iter_entry_points('qubes.tests.extra'):
         for test_case in entry.load()():
-            tests.addTests(loader.loadTestsFromTestCase(
-                type(
-                    entry.name + '_' + test_case.__name__,
-                    (test_case, ExtraTestMixin, qubes.tests.QubesTestCase),
-                    {}
-                )
-            ))
+            tests.addTests(loader.loadTestsFromTestCase(test_case))
 
     try:
         qc = qubes.qubes.QubesVmCollection()
@@ -100,8 +94,7 @@ def load_tests(loader, tests, pattern):
                     type(
                         '{}_{}_{}'.format(
                             entry.name, test_case.__name__, template),
-                        (test_case, ExtraTestMixin,
-                         qubes.tests.QubesTestCase),
+                        (test_case,),
                         {'template': template}
                     )
                 ))

tests/run.py

@@ -314,7 +314,7 @@ def main():
         for name in args.names:
             suite.addTests(
                 [test for test in list_test_cases(alltests)
-                 if (str(test)+'/').startswith(name.replace('.', '/')+'/')])
+                 if str(test).startswith(name)])
     else:
         suite.addTests(loader.loadTestsFromName('qubes.tests'))