Added integration tests for sequence builders.

pytorch_transformers/tests/tokenization_roberta_test.py

@@ -71,10 +71,22 @@ class RobertaTokenizationTest(CommonTestCases.CommonTokenizerTester):
             [0, 31414, 232, 328, 2]
         )
         self.assertListEqual(
-            tokenizer.encode('Hello world! cécé herlolip'),
+            tokenizer.encode('Hello world! cécé herlolip 418'),
             [0, 31414, 232, 328, 740, 1140, 12695, 69, 46078, 1588, 2]
         )
 
+    def test_sequence_builders(self):
+        tokenizer = RobertaTokenizer.from_pretrained("roberta-base")
+
+        text = tokenizer.encode("sequence builders")
+        text_2 = tokenizer.encode("multi-sequence build")
+
+        encoded_sentence = tokenizer.add_special_tokens_single_sentence(text)
+        encoded_pair = tokenizer.add_special_tokens_sentences_pair(text, text_2)
+
+        assert encoded_sentence == [0] + text + [2]
+        assert encoded_pair == [0] + text + [2, 2] + text_2 + [2]
+
 
 if __name__ == '__main__':
     unittest.main()