Default runtests

runtests.py

@@ -5,8 +5,11 @@ import sys
 def runtests(args=None):
     import pytest
 
-    if args is None:
-        args = ['tests']
+    if not args:
+        args = []
+
+    if not any(a for a in args[1:] if not a.startswith('-')):
+        args.append('tests')
 
     sys.exit(pytest.main(args))