add tests for issue #853 - restrictions by NULL

Author: dimitri-yatsenko

tests/schema.py

@@ -146,7 +146,7 @@ def make(self, key):
         populate with random data
         """
         from datetime import date, timedelta
-        users = User().fetch()['username']
+        users = [None, None] + list(User().fetch()['username'])
         random.seed('Amazing Seed')
         self.insert(
             dict(key,
@@ -155,7 +155,6 @@ def make(self, key):
                  username=random.choice(users))
             for experiment_id in range(self.fake_experiments_per_subject))
 
-
 @schema
 class Trial(dj.Imported):
     definition = """   # a trial within an experiment

tests/test_relational_operand.py

@@ -290,6 +290,15 @@ def test_pandas_fetch_and_restriction():
         assert_true(isinstance(df, pandas.DataFrame))
         assert_equal(len(E & q), len(E & df))
 
+    @staticmethod
+    def test_restriction_by_null():
+        assert_true(len(Experiment & 'username is null') > 0)
+        assert_true(len(Experiment & 'username is not null') > 0)
+
+    @staticmethod
+    def test_restriction_between():   # see issue
+        assert_true(len(Experiment & 'username between "S" and "Z"') < len(Experiment()))
+
     @staticmethod
     def test_restrictions_by_lists():
         x = D()