Fix json sql tests

* Make tests deterministic
* Run tests against Postgres

tests/functions/test_json_sql.py

@@ -9,23 +9,25 @@ class TestJSONSQL(TestCase):
     dns = 'postgres://postgres@localhost/sqlalchemy_utils_test'
 
     @pytest.mark.parametrize(
-        ('value', 'compiled'),
+        ('value', 'result'),
         (
-            (1, 'to_json(1)'),
+            (1, 1),
-            (14.14, 'to_json(14.14)'),
+            (14.14, 14.14),
-            ({'a': 2, 'b': 'c'}, "json_build_object('a', 2, 'b', 'c')"),
+            ({'a': 2, 'b': 'c'}, {'a': 2, 'b': 'c'}),
             (
                 {'a': {'b': 'c'}},
-                "json_build_object('a', json_build_object('b', 'c'))"
+                {'a': {'b': 'c'}}
             ),
-            ({}, 'json_build_object()'),
+            ({}, {}),
-            ([1, 2], 'json_build_array(1, 2)'),
+            ([1, 2], [1, 2]),
-            ([], 'json_build_array()'),
+            ([], []),
             (
-                [sa.select([sa.text('1')])],
+                [sa.select([sa.text('1')]).label('alias')],
-                'json_build_array((SELECT 1))'
+                [1]
             )
         )
     )
-    def test_compiled_scalars(self, value, compiled):
+    def test_compiled_scalars(self, value, result):
-        assert str(json_sql(value).compile(self.connection)) == compiled
+        assert result == (
+            self.connection.execute(sa.select([json_sql(value)])).fetchone()[0]
+        )