TST: add roundtrip check

tests/test_labelarray.py

@@ -7,6 +7,7 @@ from toolz import take
 
 from zipline.lib.labelarray import LabelArray
 from zipline.testing import check_arrays, parameter_space, ZiplineTestCase
+from zipline.testing.predicates import assert_equal
 from zipline.utils.compat import unicode
 
 
@@ -341,6 +342,15 @@ class LabelArrayTestCase(ZiplineTestCase):
         check_arrays(arr, orig_arr)
 
     def test_narrow_code_storage(self):
+        def check_roundtrip(arr):
+            assert_equal(
+                arr.as_string_array(),
+                LabelArray(
+                    arr.as_string_array(),
+                    arr.missing_value,
+                ).as_string_array(),
+            )
+
         def create_categories(width, plus_one):
             length = int(width / 8) + plus_one
             return [
@@ -359,10 +369,12 @@ class LabelArrayTestCase(ZiplineTestCase):
             categories=categories,
         )
         self.assertEqual(arr.itemsize, 1)
+        check_roundtrip(arr)
 
         # uint8 inference
         arr = LabelArray(categories, missing_value=categories[0])
         self.assertEqual(arr.itemsize, 1)
+        check_roundtrip(arr)
 
         # just over uint8
         categories = create_categories(8, plus_one=True)
@@ -372,10 +384,12 @@ class LabelArrayTestCase(ZiplineTestCase):
             categories=categories,
         )
         self.assertEqual(arr.itemsize, 2)
+        check_roundtrip(arr)
 
         # uint16 inference
         arr = LabelArray(categories, missing_value=categories[0])
         self.assertEqual(arr.itemsize, 2)
+        check_roundtrip(arr)
 
         # fits in uint16
         categories = create_categories(16, plus_one=False)
@@ -384,10 +398,12 @@ class LabelArrayTestCase(ZiplineTestCase):
             categories=categories,
         )
         self.assertEqual(arr.itemsize, 2)
+        check_roundtrip(arr)
 
         # uint16 inference
         arr = LabelArray(categories, missing_value=categories[0])
         self.assertEqual(arr.itemsize, 2)
+        check_roundtrip(arr)
 
         # just over uint16
         categories = create_categories(16, plus_one=True)
@@ -397,10 +413,12 @@ class LabelArrayTestCase(ZiplineTestCase):
             categories=categories,
         )
         self.assertEqual(arr.itemsize, 4)
+        check_roundtrip(arr)
 
         # uint32 inference
         arr = LabelArray(categories, missing_value=categories[0])
         self.assertEqual(arr.itemsize, 4)
+        check_roundtrip(arr)
 
         # NOTE: we could do this for 32 and 64; however, no one has enough RAM
         # or time for that.