[tests] Safety checks on CONFIG_MAPPING

tests/test_configuration_auto.py

@@ -16,7 +16,7 @@
 import os
 import unittest
 
-from transformers.configuration_auto import AutoConfig
+from transformers.configuration_auto import CONFIG_MAPPING, AutoConfig
 from transformers.configuration_bert import BertConfig
 from transformers.configuration_roberta import RobertaConfig
 
@@ -42,3 +42,13 @@ class AutoConfigTest(unittest.TestCase):
     def test_config_for_model_str(self):
         config = AutoConfig.for_model("roberta")
         self.assertIsInstance(config, RobertaConfig)
+
+    def test_pattern_matching_fallback(self):
+        """
+        In cases where config.json doesn't include a model_type,
+        perform a few safety checks on the config mapping's order.
+        """
+        # no key string should be included in a later key string (typical failure case)
+        keys = list(CONFIG_MAPPING.keys())
+        for i, key in enumerate(keys):
+            self.assertFalse(any(key in later_key for later_key in keys[i+1:]))