fixing sqlalchemy empty() test case

requirements-dev.txt

@@ -1,4 +1,5 @@
 -r requirements.txt
+alchemy-mock
 coreapi
 coverage
 django-extensions

tests/backends/test_sqlalchemy.py

@@ -3,8 +3,8 @@
 
 import pytest
 import six
+from alchemy_mock.comparison import ExpressionMatcher
 from sqlalchemy import func
-from sqlalchemy.sql.elements import ClauseList, Grouping
 from sqlalchemy.types import String
 
 from test_project.one_to_one.alchemy import Place, Restaurant, Waiter
@@ -13,20 +13,7 @@
 
 
 def assert_alchemy_expressions_equal(exp1, exp2):
-    assert six.text_type(exp1) == six.text_type(exp2)
-
-    if isinstance(exp1.right, Grouping):
-        values1 = list(i.value for i in exp1.right.element.clauses)
-        values2 = list(i.value for i in exp2.right.element.clauses)
-        assert values1 == values2
-
-    elif isinstance(exp1.right, ClauseList):
-        values1 = list(i.value for i in exp1.right.clauses)
-        values2 = list(i.value for i in exp2.right.clauses)
-        assert values1 == values2
-
-    elif hasattr(exp1.right, 'value'):
-        assert exp1.right.value == exp2.right.value
+    assert ExpressionMatcher(exp1) == exp2
 
 
 class TestSQLAlchemyFilterBackend(object):
@@ -50,7 +37,7 @@ def test_empty(self, alchemy_db):
             context={'context': 'here'},
         )
 
-        assert backend.empty().count() == 0
+        assert 'WHERE 0 = 1' in six.text_type(backend.empty())
 
     def test_get_model(self, alchemy_db):
         backend = SQLAlchemyFilterBackend(alchemy_db.query(Place))