Add xfailing test for #3468

spacy/tests/regression/test_issue3468.py

@@ -0,0 +1,23 @@
+# coding: utf8
+from __future__ import unicode_literals
+
+import pytest
+from spacy.lang.en import English
+from spacy.tokens import Doc
+
+
+@pytest.mark.xfail
+def test_issue3468():
+    """Test that sentence boundaries are serialized if they're not set by the
+    dependency parser."""
+    nlp = English()
+    nlp.add_pipe(nlp.create_pipe("sentencizer"))
+    doc = nlp("Hello world")
+    assert doc.is_sentenced
+    assert doc[0].is_sent_start
+    assert len(list(doc.sents)) == 1
+    doc_bytes = doc.to_bytes()
+    new_doc = Doc(nlp.vocab).from_bytes(doc_bytes)
+    assert new_doc.is_sentenced
+    assert doc[0].is_sent_start
+    assert len(list(new_doc.sents)) == 1