Add slow generate tests for pretrained lm models (#2909)

* add slow generate lm_model tests

* fix conflicts

* merge conflicts

* fix conflicts

* add slow generate lm_model tests

* make style

* delete unused variable

* fix conflicts

* fix conflicts

* fix conflicts

* delete unused variable

* fix conflicts

* finished hard coded tests

tests/test_modeling_openai.py

@@ -24,6 +24,7 @@ from .utils import CACHE_DIR, require_torch, slow, torch_device
 
 
 if is_torch_available():
+    import torch
     from transformers import (
         OpenAIGPTConfig,
         OpenAIGPTModel,
@@ -208,3 +209,36 @@ class OpenAIGPTModelTest(ModelTesterMixin, unittest.TestCase):
         for model_name in list(OPENAI_GPT_PRETRAINED_MODEL_ARCHIVE_MAP.keys())[:1]:
             model = OpenAIGPTModel.from_pretrained(model_name, cache_dir=CACHE_DIR)
             self.assertIsNotNone(model)
+
+
+class OPENAIGPTModelLanguageGenerationTest(unittest.TestCase):
+    @slow
+    def test_lm_generate_openai_gpt(self):
+        model = OpenAIGPTLMHeadModel.from_pretrained("openai-gpt")
+        input_ids = torch.Tensor([[481, 2585, 544, 4957]]).long()  # The dog is cute
+        expected_output_ids = [
+            481,
+            2585,
+            544,
+            4957,
+            669,
+            512,
+            761,
+            5990,
+            271,
+            645,
+            487,
+            535,
+            976,
+            2479,
+            240,
+            487,
+            804,
+            1296,
+            2891,
+            512,
+        ]  # the dog is cute when you're annoyed : if he's really stupid, he 'll stop fighting you
+        torch.manual_seed(0)
+
+        output_ids = model.generate(input_ids)
+        self.assertListEqual(output_ids[0].tolist(), expected_output_ids)