Add test for issue 3209

spacy/tests/regression/test_issue3209.py

@@ -0,0 +1,22 @@
+'''Test that labels are mapped to classes consistently when loading NER model.'''
+from __future__ import unicode_literals
+from spacy.lang.en import English
+
+def test_issue3209():
+    '''Test issue that occurred in spaCy nightly where NER labels were being
+    mapped to classes incorrectly after loading the model, when the labels
+    were added using ner.add_label().
+    '''
+    nlp = English()
+    ner = nlp.create_pipe('ner')
+    nlp.add_pipe(ner)
+    
+    ner.add_label('ANIMAL')
+    nlp.begin_training()
+    move_names = ['O', 'B-ANIMAL', 'I-ANIMAL', 'L-ANIMAL', 'U-ANIMAL']
+    assert ner.move_names == move_names
+    nlp2 = English()
+    nlp2.add_pipe(nlp2.create_pipe('ner'))
+    nlp2.from_bytes(nlp.to_bytes())
+    assert nlp2.get_pipe('ner').move_names == move_names
+