move test to proper file

Lib/test/test_collections.py

@@ -70,17 +70,6 @@ class TestUserObjects(unittest.TestCase):
         obj[123] = "abc"
         self._copy_test(obj)
 
-    def test_str_rmod(self):
-        class ustr2(UserString):
-            pass
-
-        class ustr3(ustr2):
-            def __rmod__(self, other):
-                return super().__rmod__(other)
-
-        fmt2 = ustr2('value is %s')
-        str3 = ustr3('TEST')
-        self.assertEqual(fmt2 % str3, 'value is TEST')
 
 ################################################################################
 ### ChainMap (helper class for configparser and the string module)

Lib/test/test_userstring.py

@@ -39,6 +39,18 @@ class UserStringTest(
         # we don't fix the arguments, because UserString can't cope with it
         getattr(object, methodname)(*args)
 
+    def test_rmod(self):
+        class ustr2(UserString):
+            pass
+
+        class ustr3(ustr2):
+            def __rmod__(self, other):
+                return super().__rmod__(other)
+
+        fmt2 = ustr2('value is %s')
+        str3 = ustr3('TEST')
+        self.assertEqual(fmt2 % str3, 'value is TEST')
+
 
 if __name__ == "__main__":
     unittest.main()