Specify individual long tests to run

The test script currently only allows to run all the long test. This
change will allow a user to specify individual long tests to run.

system/run.py

@@ -73,6 +73,7 @@ if __name__ == "__main__":
     if len(sys.argv) > 1:
         if sys.argv[1] == "--long":
             include_long_tests = True
+            tests = sys.argv[2:]
         else:
             tests = sys.argv[1:]
     run(include_long_tests, tests)