Update regression test

spacy/tests/regression/test_issue636.py

@@ -0,0 +1,16 @@
+# coding: utf8
+from __future__ import unicode_literals
+
+from ...tokens.doc import Doc
+import pytest
+
+
+@pytest.mark.xfail
+@pytest.mark.models
+@pytest.mark.parametrize('text', ["I cant do this."])
+def test_issue636(EN, text):
+    """Test that to_bytes and from_bytes don't change the token lemma."""
+    doc1 = EN(text)
+    doc2 = Doc(EN.vocab)
+    doc2.from_bytes(doc1.to_bytes())
+    assert doc1[2].lemma_ == doc2[2].lemma_