Expose get_config() on ModelTesters (#12812)

* Expose get_config() on ModelTesters

* Typo

tests/test_modeling_bert_generation.py

@@ -16,7 +16,7 @@
 
 import unittest
 
-from transformers import is_torch_available
+from transformers import BertGenerationConfig, is_torch_available
 from transformers.testing_utils import require_torch, slow, torch_device
 
 from .test_configuration_common import ConfigTester
@@ -27,7 +27,7 @@ from .test_modeling_common import ModelTesterMixin, floats_tensor, ids_tensor, r
 if is_torch_available():
     import torch
 
-    from transformers import BertGenerationConfig, BertGenerationDecoder, BertGenerationEncoder
+    from transformers import BertGenerationDecoder, BertGenerationEncoder
 
 
 class BertGenerationEncoderTester:
@@ -79,7 +79,12 @@ class BertGenerationEncoderTester:
         if self.use_labels:
             token_labels = ids_tensor([self.batch_size, self.seq_length], self.vocab_size)
 
-        config = BertGenerationConfig(
+        config = self.get_config()
+
+        return config, input_ids, input_mask, token_labels
+
+    def get_config(self):
+        return BertGenerationConfig(
             vocab_size=self.vocab_size,
             hidden_size=self.hidden_size,
             num_hidden_layers=self.num_hidden_layers,
@@ -93,8 +98,6 @@ class BertGenerationEncoderTester:
             initializer_range=self.initializer_range,
         )
 
-        return config, input_ids, input_mask, token_labels
-
     def prepare_config_and_inputs_for_decoder(self):
         (
             config,