Fix broken MergeByTypeTarge.identity function

Pending: I still need to investigate why the existing tests didn't catch
this.

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

src/frequenz/dispatch/_merge_strategies.py

@@ -64,4 +64,4 @@ class MergeByTypeTarget(MergeByType):
     @override
     def identity(self, dispatch: Dispatch) -> int:
         """Identity function for the merge criteria."""
-        return hash((dispatch.type, dispatch.target))
+        return hash((dispatch.type, tuple(dispatch.target)))

tests/test_frequenz_dispatch.py

@@ -24,6 +24,7 @@
     Deleted,
     Dispatch,
     DispatchEvent,
+    MergeByIdentity,
     MergeByType,
     MergeByTypeTarget,
     MergeStrategy,
@@ -678,7 +679,7 @@ async def test_multiple_dispatches_sequential_intervals_merge(
 async def test_at_least_one_running_filter(
     fake_time: time_machine.Coordinates,
     generator: DispatchGenerator,
-    merge_strategy: MergeStrategy,
+    merge_strategy: MergeByIdentity,
 ) -> None:
     """Test scenarios directly tied to the _at_least_one_running logic."""
     microgrid_id = randint(1, 100)
@@ -701,6 +702,8 @@ async def test_at_least_one_running_filter(
         recurrence=RecurrenceRule(),
         type="TEST_TYPE",
     )
+    _ = merge_strategy.identity(Dispatch(dispatch))
+
     lifecycle = service.new_lifecycle_events_receiver("TEST_TYPE")
     await client.create(**to_create_params(microgrid_id, dispatch))
     await lifecycle.receive()