diff --git a/tests/partitionedjobs/test_crossbackend.py b/tests/partitionedjobs/test_crossbackend.py
index 28a10e8..1deb3bc 100644
--- a/tests/partitionedjobs/test_crossbackend.py
+++ b/tests/partitionedjobs/test_crossbackend.py
@@ -1048,3 +1048,35 @@ def test_triple_split(self):
                 _SubGraphData(split_node="merge1", node_ids={"bands1", "merge1", "temporal2", "lc2"}, backend_id="b2"),
             ],
         )
+
+    @pytest.mark.parametrize(
+        ["primary_backend", "secondary_graph"],
+        [
+            ("b1", _SubGraphData(split_node="lc2", node_ids={"lc2"}, backend_id="b2")),
+            ("b2", _SubGraphData(split_node="lc1", node_ids={"lc1"}, backend_id="b1")),
+        ],
+    )
+    def test_split_with_primary_backend(self, primary_backend, secondary_graph):
+        """Test `primary_backend` argument of DeepGraphSplitter"""
+        splitter = DeepGraphSplitter(
+            supporting_backends=supporting_backends_from_node_id_dict({"lc1": ["b1"], "lc2": ["b2"]}),
+            primary_backend=primary_backend,
+        )
+        flat = {
+            #   lc1   lc2
+            #      \ /
+            #     merge
+            "lc1": {"process_id": "load_collection", "arguments": {"id": "S1"}},
+            "lc2": {"process_id": "load_collection", "arguments": {"id": "S2"}},
+            "merge": {
+                "process_id": "merge_cubes",
+                "arguments": {"cube1": {"from_node": "lc1"}, "cube2": {"from_node": "lc2"}},
+                "result": True,
+            },
+        }
+        result = splitter.split(flat)
+        assert result == _PGSplitResult(
+            primary_node_ids={"lc1", "lc2", "merge"},
+            primary_backend_id=primary_backend,
+            secondary_graphs=[secondary_graph],
+        )