fix: first callback execution

elastica/modules/callbacks.py

@@ -74,6 +74,9 @@ def _finalize_callback(self: SystemCollectionProtocol) -> None:
         self._callback_list.clear()
         del self._callback_list
 
+        # First callback execution
+        self.apply_callbacks(time=np.float64(0.0), current_step=0)
+
 
 class _CallBack:
     """

tests/test_modules/test_callbacks.py

@@ -184,3 +184,18 @@ def test_callback_finalize_sorted(self, load_rod_with_callbacks):
         for x, _ in scwc._callback_list:
             assert num < x
             num = x
+
+    def test_first_call_callback_during_finalize(self, mocker, load_rod_with_callbacks):
+        """
+        This test is to check if the callback is called during the finalize.
+        If this test fails, check if `apply_callbacks` is called during the finalization step.
+        """
+        scwc, callback_cls = load_rod_with_callbacks
+        callback_features = [d for d in scwc._callback_list]
+
+        spy = mocker.spy(scwc, "apply_callbacks")
+        scwc._finalize_callback()
+
+        assert spy.call_count == 1
+        assert spy.call_args[1]["time"] == np.float64(0.0)
+        assert spy.call_args[1]["current_step"] == 0