Add unit test.

Author: WaVEV

tests/lookup_/tests.py

@@ -66,3 +66,51 @@ def test_eq_and_in(self):
             "lookup__book",
             [{"$match": {"$and": [{"isbn": {"$in": ("12345", "56789")}}, {"title": "Moby Dick"}]}}],
         )
+
+    def test_union_simple_conditions(self):
+        with self.assertNumQueries(1) as ctx:
+            list(Book.objects.filter(title="star wars").union(Book.objects.filter(isbn__in="1234")))
+        self.assertAggregateQuery(
+            ctx.captured_queries[0]["sql"],
+            "lookup__book",
+            [
+                {"$match": {"title": "star wars"}},
+                {"$project": {"_id": 1, "title": 1, "isbn": 1}},
+                {
+                    "$unionWith": {
+                        "coll": "lookup__book",
+                        "pipeline": [
+                            {"$match": {"isbn": {"$in": ("1", "2", "3", "4")}}},
+                            {"$project": {"_id": 1, "title": 1, "isbn": 1}},
+                        ],
+                    }
+                },
+                {"$group": {"_id": {"_id": "$_id", "title": "$title", "isbn": "$isbn"}}},
+                {"$addFields": {"_id": "$_id._id", "title": "$_id.title", "isbn": "$_id.isbn"}},
+            ],
+        )
+
+    def test_union_all_simple_conditions(self):
+        with self.assertNumQueries(1) as ctx:
+            list(
+                Book.objects.filter(title="star wars").union(
+                    Book.objects.filter(isbn="1234"), all=True
+                )
+            )
+        self.assertAggregateQuery(
+            ctx.captured_queries[0]["sql"],
+            "lookup__book",
+            [
+                {"$match": {"title": "star wars"}},
+                {"$project": {"_id": 1, "title": 1, "isbn": 1}},
+                {
+                    "$unionWith": {
+                        "coll": "lookup__book",
+                        "pipeline": [
+                            {"$match": {"isbn": "1234"}},
+                            {"$project": {"_id": 1, "title": 1, "isbn": 1}},
+                        ],
+                    }
+                },
+            ],
+        )