diff --git a/rsconcept/backend/apps/oss/models/OperationSchema.py b/rsconcept/backend/apps/oss/models/OperationSchema.py
index 39eeae94..86120a06 100644
--- a/rsconcept/backend/apps/oss/models/OperationSchema.py
+++ b/rsconcept/backend/apps/oss/models/OperationSchema.py
@@ -131,56 +131,73 @@ class OperationSchema:
             self.after_create_cst(list(rsform.constituents()), rsform)
         self.save(update_fields=['time_update'])
 
-    def set_arguments(self, operation: Operation, arguments: list[Operation]) -> None:
+    def set_arguments(self, target: int, arguments: list[Operation]) -> None:
         ''' Set arguments to operation. '''
+        self.cache.ensure_loaded()
+        operation = self.cache.operation_by_id[target]
         processed: list[Operation] = []
-        changed = False
+        deleted: list[Argument] = []
         for current in operation.getArguments():
             if current.argument not in arguments:
-                changed = True
-                current.delete()
+                deleted.append(current)
             else:
                 processed.append(current.argument)
+        if len(deleted) > 0:
+            self.before_delete_arguments(operation, [x.argument for x in deleted])
+            for deleted_arg in deleted:
+                self.cache.remove_argument(deleted_arg)
+            Argument.objects.filter(pk__in=[x.pk for x in deleted]).delete()
+
+        added: list[Operation] = []
         for arg in arguments:
             if arg not in processed:
-                changed = True
                 processed.append(arg)
-                Argument.objects.create(operation=operation, argument=arg)
-        if not changed:
-            return
-        # TODO: trigger on_change effects
-        self.save(update_fields=['time_update'])
+                new_arg = Argument.objects.create(operation=operation, argument=arg)
+                self.cache.insert_argument(new_arg)
+                added.append(arg)
+        if len(added) > 0:
+            self.after_create_arguments(operation, added)
+        if len(added) > 0 or len(deleted) > 0:
+            self.save(update_fields=['time_update'])
 
-    def set_substitutions(self, target: Operation, substitutes: list[dict]) -> None:
+    def set_substitutions(self, target: int, substitutes: list[dict]) -> None:
         ''' Clear all arguments for operation. '''
+        self.cache.ensure_loaded()
+        operation = self.cache.operation_by_id[target]
+        schema = self.cache.get_schema(operation)
         processed: list[dict] = []
-        changed = False
-
-        for current in target.getSubstitutions():
+        deleted: list[Substitution] = []
+        for current in operation.getSubstitutions():
             subs = [
                 x for x in substitutes
                 if x['original'] == current.original and x['substitution'] == current.substitution
             ]
             if len(subs) == 0:
-                changed = True
-                current.delete()
+                deleted.append(current)
             else:
                 processed.append(subs[0])
+        if len(deleted) > 0:
+            if schema is not None:
+                for sub in deleted:
+                    self._undo_substitution(sub, schema)
+            else:
+                for sub in deleted:
+                    self.cache.remove_substitution(sub)
+                Substitution.objects.filter(pk__in=[x.pk for x in deleted]).delete()
 
-        for sub in substitutes:
-            if sub not in processed:
-                changed = True
-                Substitution.objects.create(
-                    operation=target,
-                    original=sub['original'],
-                    substitution=sub['substitution']
+        added: list[Substitution] = []
+        for sub_item in substitutes:
+            if sub_item not in processed:
+                new_sub = Substitution.objects.create(
+                    operation=operation,
+                    original=sub_item['original'],
+                    substitution=sub_item['substitution']
                 )
+                added.append(new_sub)
+        self._process_added_substitutions(added, schema)
 
-        if not changed:
-            return
-        # TODO: trigger on_change effects
-
-        self.save(update_fields=['time_update'])
+        if len(added) > 0 or len(deleted) > 0:
+            self.save(update_fields=['time_update'])
 
     def create_input(self, operation: Operation) -> RSForm:
         ''' Create input RSForm. '''
@@ -242,7 +259,7 @@ class OperationSchema:
 
     def after_create_cst(self, cst_list: list[Constituenta], source: RSForm) -> None:
         ''' Trigger cascade resolutions when new constituent is created. '''
-        self.cache.insert(source)
+        self.cache.insert_schema(source)
         inserted_aliases = [cst.alias for cst in cst_list]
         depend_aliases: set[str] = set()
         for new_cst in cst_list:
@@ -258,13 +275,13 @@ class OperationSchema:
 
     def after_change_cst_type(self, target: Constituenta, source: RSForm) -> None:
         ''' Trigger cascade resolutions when constituenta type is changed. '''
-        self.cache.insert(source)
+        self.cache.insert_schema(source)
         operation = self.cache.get_operation(source.model.pk)
         self._cascade_change_cst_type(target.pk, target.cst_type, operation.pk)
 
     def after_update_cst(self, target: Constituenta, data: dict, old_data: dict, source: RSForm) -> None:
         ''' Trigger cascade resolutions when constituenta data is changed. '''
-        self.cache.insert(source)
+        self.cache.insert_schema(source)
         operation = self.cache.get_operation(source.model.pk)
         depend_aliases = self._extract_data_references(data, old_data)
         alias_mapping: CstMapping = {}
@@ -282,16 +299,26 @@ class OperationSchema:
 
     def before_delete_cst(self, target: list[Constituenta], source: RSForm) -> None:
         ''' Trigger cascade resolutions before constituents are deleted. '''
-        self.cache.insert(source)
+        self.cache.insert_schema(source)
         operation = self.cache.get_operation(source.model.pk)
         self._cascade_before_delete(target, operation.pk)
 
     def before_substitute(self, substitutions: CstSubstitution, source: RSForm) -> None:
         ''' Trigger cascade resolutions before constituents are substituted. '''
-        self.cache.insert(source)
+        self.cache.insert_schema(source)
         operation = self.cache.get_operation(source.model.pk)
         self._cascade_before_substitute(substitutions, operation)
 
+    def before_delete_arguments(self, target: Operation, arguments: list[Operation]) -> None:
+        ''' Trigger cascade resolutions before arguments are deleted. '''
+        pass
+
+    def after_create_arguments(self, target: Operation, arguments: list[Operation]) -> None:
+        ''' Trigger cascade resolutions after arguments are created. '''
+        schema = self.cache.get_schema(target)
+        if schema is None:
+            return
+
     def _cascade_create_cst(self, cst_list: list[Constituenta], operation: Operation, mapping: CstMapping) -> None:
         children = self.cache.graph.outputs[operation.pk]
         if len(children) == 0:
@@ -411,12 +438,12 @@ class OperationSchema:
         self,
         mapping: CstMapping,
         target: list[int],
-        operation: Operation,
+        operation: int,
         schema: RSForm
     ) -> None:
         alias_mapping = OperationSchema._produce_alias_mapping(mapping)
         schema.apply_partial_mapping(alias_mapping, target)
-        children = self.cache.graph.outputs[operation.pk]
+        children = self.cache.graph.outputs[operation]
         if len(children) == 0:
             return
         self.cache.ensure_loaded()
@@ -431,7 +458,7 @@ class OperationSchema:
             new_target = self.cache.get_inheritors_list(target, child_id)
             if len(new_target) == 0:
                 continue
-            self._cascade_partial_mapping(new_mapping, new_target, child_operation, child_schema)
+            self._cascade_partial_mapping(new_mapping, new_target, child_id, child_schema)
 
     @staticmethod
     def _produce_alias_mapping(mapping: CstMapping) -> dict[str, str]:
@@ -557,35 +584,64 @@ class OperationSchema:
         for sub in to_process:
             self._undo_substitution(sub, schema, target_ids)
 
-    def _undo_substitution(self, target: Substitution, schema: RSForm, ignore_parents: list[int]) -> None:
-        operation = self.cache.operation_by_id[target.operation_id]
+    def _undo_substitution(
+        self,
+        target: Substitution,
+        schema: RSForm,
+        ignore_parents: Optional[list[int]] = None
+    ) -> None:
+        if ignore_parents is None:
+            ignore_parents = []
+        operation_id = target.operation_id
         original_schema, _, original_cst, substitution_cst = self.cache.unfold_sub(target)
 
         dependant = []
         for cst_id in original_schema.get_dependant([original_cst.pk]):
             if cst_id not in ignore_parents:
-                inheritor_id = self.cache.get_inheritor(cst_id, operation.pk)
+                inheritor_id = self.cache.get_inheritor(cst_id, operation_id)
                 if inheritor_id is not None:
                     dependant.append(inheritor_id)
 
-        self.cache.substitutions[operation.pk].remove(target)
+        self.cache.substitutions[operation_id].remove(target)
         target.delete()
 
         new_original: Optional[Constituenta] = None
         if original_cst.pk not in ignore_parents:
             full_cst = Constituenta.objects.get(pk=original_cst.pk)
             self.after_create_cst([full_cst], original_schema)
-            new_original_id = self.cache.get_inheritor(original_cst.pk, operation.pk)
+            new_original_id = self.cache.get_inheritor(original_cst.pk, operation_id)
             assert new_original_id is not None
             new_original = schema.cache.by_id[new_original_id]
         if len(dependant) == 0:
             return
 
-        substitution_id = self.cache.get_inheritor(substitution_cst.pk, operation.pk)
+        substitution_id = self.cache.get_inheritor(substitution_cst.pk, operation_id)
         assert substitution_id is not None
         substitution_inheritor = schema.cache.by_id[substitution_id]
         mapping = {cast(str, substitution_inheritor.alias): new_original}
-        self._cascade_partial_mapping(mapping, dependant, operation, schema)
+        self._cascade_partial_mapping(mapping, dependant, operation_id, schema)
+
+    def _process_added_substitutions(self, added: list[Substitution], schema: Optional[RSForm]) -> None:
+        if len(added) == 0:
+            return
+        if schema is None:
+            for sub in added:
+                self.cache.insert_substitution(sub)
+            return
+
+        cst_mapping: CstSubstitution = []
+        for sub in added:
+            original_id = self.cache.get_inheritor(sub.original_id, sub.operation_id)
+            substitution_id = self.cache.get_inheritor(sub.substitution_id, sub.operation_id)
+            if original_id is None or substitution_id is None:
+                raise ValueError('Substitutions not found.')
+            original_cst = schema.cache.by_id[original_id]
+            substitution_cst = schema.cache.by_id[substitution_id]
+            cst_mapping.append((original_cst, substitution_cst))
+        self.before_substitute(cst_mapping, schema)
+        schema.substitute(cst_mapping)
+        for sub in added:
+            self.cache.insert_substitution(sub)
 
 
 class OssCache:
@@ -608,11 +664,18 @@ class OssCache:
         self.substitutions: dict[int, list[Substitution]] = {}
         self.inheritance: dict[int, list[Inheritance]] = {}
 
-    def insert(self, schema: RSForm) -> None:
-        ''' Insert new schema. '''
-        if not self._schema_by_id.get(schema.model.pk):
-            schema.cache.ensure_loaded()
-            self._insert_new(schema)
+    def ensure_loaded(self) -> None:
+        ''' Ensure cache is fully loaded. '''
+        if self.is_loaded:
+            return
+        self.is_loaded = True
+        for operation in self.operations:
+            self.inheritance[operation.pk] = []
+            self.substitutions[operation.pk] = []
+        for sub in self._oss.substitutions().only('operation_id', 'original_id', 'substitution_id'):
+            self.substitutions[sub.operation_id].append(sub)
+        for item in self._oss.inheritance().only('operation_id', 'parent_id', 'child_id'):
+            self.inheritance[item.operation_id].append(item)
 
     def get_schema(self, operation: Operation) -> Optional[RSForm]:
         ''' Get schema by Operation. '''
@@ -633,19 +696,6 @@ class OssCache:
                 return operation
         raise ValueError(f'Operation for schema {schema} not found')
 
-    def ensure_loaded(self) -> None:
-        ''' Ensure cache is fully loaded. '''
-        if self.is_loaded:
-            return
-        self.is_loaded = True
-        for operation in self.operations:
-            self.inheritance[operation.pk] = []
-            self.substitutions[operation.pk] = []
-        for sub in self._oss.substitutions().only('operation_id', 'original_id', 'substitution_id'):
-            self.substitutions[sub.operation_id].append(sub)
-        for item in self._oss.inheritance().only('operation_id', 'parent_id', 'child_id'):
-            self.inheritance[item.operation_id].append(item)
-
     def get_inheritor(self, parent_cst: int, operation: int) -> Optional[int]:
         ''' Get child for parent inside target RSFrom. '''
         for item in self.inheritance[operation]:
@@ -668,6 +718,12 @@ class OssCache:
                 return self.get_inheritor(sub.substitution_id, operation)
         return self.get_inheritor(parent_cst, operation)
 
+    def insert_schema(self, schema: RSForm) -> None:
+        ''' Insert new schema. '''
+        if not self._schema_by_id.get(schema.model.pk):
+            schema.cache.ensure_loaded()
+            self._insert_new(schema)
+
     def insert_operation(self, operation: Operation) -> None:
         ''' Insert new operation. '''
         self.operations.append(operation)
@@ -677,6 +733,10 @@ class OssCache:
             self.substitutions[operation.pk] = []
             self.inheritance[operation.pk] = []
 
+    def insert_argument(self, argument: Argument) -> None:
+        ''' Insert new argument. '''
+        self.graph.add_edge(argument.operation_id, argument.argument_id)
+
     def insert_inheritance(self, inheritance: Inheritance) -> None:
         ''' Insert new inheritance. '''
         self.inheritance[inheritance.operation_id].append(inheritance)
@@ -697,9 +757,15 @@ class OssCache:
         for item in inherit_to_delete:
             self.inheritance[operation].remove(item)
 
+    def remove_schema(self, schema: RSForm) -> None:
+        ''' Remove schema from cache. '''
+        self._schemas.remove(schema)
+        del self._schema_by_id[schema.model.pk]
+
     def remove_operation(self, operation: int) -> None:
         ''' Remove operation from cache. '''
         target = self.operation_by_id[operation]
+        self.graph.remove_node(operation)
         if target.result_id in self._schema_by_id:
             self._schemas.remove(self._schema_by_id[target.result_id])
             del self._schema_by_id[target.result_id]
@@ -709,10 +775,13 @@ class OssCache:
             del self.substitutions[operation]
             del self.inheritance[operation]
 
-    def remove_schema(self, schema: RSForm) -> None:
-        ''' Remove schema from cache. '''
-        self._schemas.remove(schema)
-        del self._schema_by_id[schema.model.pk]
+    def remove_argument(self, argument: Argument) -> None:
+        ''' Remove argument from cache. '''
+        self.graph.remove_edge(argument.operation_id, argument.argument_id)
+
+    def remove_substitution(self, target: Substitution) -> None:
+        ''' Remove substitution from cache. '''
+        self.substitutions[target.operation_id].remove(target)
 
     def unfold_sub(self, sub: Substitution) -> tuple[RSForm, RSForm, Constituenta, Constituenta]:
         operation = self.operation_by_id[sub.operation_id]
diff --git a/rsconcept/backend/apps/oss/tests/s_propagation/t_constituents.py b/rsconcept/backend/apps/oss/tests/s_propagation/t_constituents.py
index 0d9ec899..a7b9f559 100644
--- a/rsconcept/backend/apps/oss/tests/s_propagation/t_constituents.py
+++ b/rsconcept/backend/apps/oss/tests/s_propagation/t_constituents.py
@@ -51,7 +51,7 @@ class TestChangeConstituents(EndpointTester):
             alias='3',
             operation_type=OperationType.SYNTHESIS
         )
-        self.owned.set_arguments(self.operation3, [self.operation1, self.operation2])
+        self.owned.set_arguments(self.operation3.pk, [self.operation1, self.operation2])
         self.owned.execute_operation(self.operation3)
         self.operation3.refresh_from_db()
         self.ks3 = RSForm(self.operation3.result)
diff --git a/rsconcept/backend/apps/oss/tests/s_propagation/t_operations.py b/rsconcept/backend/apps/oss/tests/s_propagation/t_operations.py
index 987030b3..b95c5319 100644
--- a/rsconcept/backend/apps/oss/tests/s_propagation/t_operations.py
+++ b/rsconcept/backend/apps/oss/tests/s_propagation/t_operations.py
@@ -71,8 +71,8 @@ class TestChangeOperations(EndpointTester):
             alias='4',
             operation_type=OperationType.SYNTHESIS
         )
-        self.owned.set_arguments(self.operation4, [self.operation1, self.operation2])
-        self.owned.set_substitutions(self.operation4, [{
+        self.owned.set_arguments(self.operation4.pk, [self.operation1, self.operation2])
+        self.owned.set_substitutions(self.operation4.pk, [{
             'original': self.ks1X1,
             'substitution': self.ks2S1
         }])
@@ -92,8 +92,8 @@ class TestChangeOperations(EndpointTester):
             alias='5',
             operation_type=OperationType.SYNTHESIS
         )
-        self.owned.set_arguments(self.operation5, [self.operation4, self.operation3])
-        self.owned.set_substitutions(self.operation5, [{
+        self.owned.set_arguments(self.operation5.pk, [self.operation4, self.operation3])
+        self.owned.set_substitutions(self.operation5.pk, [{
             'original': self.ks4X1,
             'substitution': self.ks3X1
         }])
@@ -249,3 +249,38 @@ class TestChangeOperations(EndpointTester):
         self.assertEqual(self.ks5.constituents().count(), 8)
         self.assertEqual(self.ks4D2.definition_formal, r'X1 X2 X3 S1 D1')
         self.assertEqual(self.ks5D4.definition_formal, r'X1 X2 X3 S1 D1 D2 D3')
+
+    @decl_endpoint('/api/oss/{item}/update-operation', method='patch')
+    def test_change_substitutions(self):
+        data = {
+            'target': self.operation4.pk,
+            'item_data': {
+                'alias': 'Test4 mod',
+                'title': 'Test title mod',
+                'comment': 'Comment mod'
+            },
+            'positions': [],
+            'arguments': [self.operation1.pk, self.operation2.pk],
+            'substitutions': [
+                {
+                    'original': self.ks1X1.pk,
+                    'substitution': self.ks2X2.pk
+                },
+                {
+                    'original': self.ks2X1.pk,
+                    'substitution': self.ks1D1.pk
+                }
+            ]
+        }
+
+        self.executeOK(data=data, item=self.owned_id)
+        self.ks4D2.refresh_from_db()
+        self.ks5D4.refresh_from_db()
+        subs1_2 = self.operation4.getSubstitutions()
+        self.assertEqual(subs1_2.count(), 2)
+        subs3_4 = self.operation5.getSubstitutions()
+        self.assertEqual(subs3_4.count(), 1)
+        self.assertEqual(self.ks4.constituents().count(), 5)
+        self.assertEqual(self.ks5.constituents().count(), 7)
+        self.assertEqual(self.ks4D2.definition_formal, r'X1 D1 X3 S1 D1')
+        self.assertEqual(self.ks5D4.definition_formal, r'X1 D2 X3 S1 D1 D2 D3')
diff --git a/rsconcept/backend/apps/oss/tests/s_propagation/t_substitutions.py b/rsconcept/backend/apps/oss/tests/s_propagation/t_substitutions.py
index 7cc5ae26..1a383a42 100644
--- a/rsconcept/backend/apps/oss/tests/s_propagation/t_substitutions.py
+++ b/rsconcept/backend/apps/oss/tests/s_propagation/t_substitutions.py
@@ -71,8 +71,8 @@ class TestChangeSubstitutions(EndpointTester):
             alias='4',
             operation_type=OperationType.SYNTHESIS
         )
-        self.owned.set_arguments(self.operation4, [self.operation1, self.operation2])
-        self.owned.set_substitutions(self.operation4, [{
+        self.owned.set_arguments(self.operation4.pk, [self.operation1, self.operation2])
+        self.owned.set_substitutions(self.operation4.pk, [{
             'original': self.ks1X1,
             'substitution': self.ks2S1
         }])
@@ -92,8 +92,8 @@ class TestChangeSubstitutions(EndpointTester):
             alias='5',
             operation_type=OperationType.SYNTHESIS
         )
-        self.owned.set_arguments(self.operation5, [self.operation4, self.operation3])
-        self.owned.set_substitutions(self.operation5, [{
+        self.owned.set_arguments(self.operation5.pk, [self.operation4, self.operation3])
+        self.owned.set_substitutions(self.operation5.pk, [{
             'original': self.ks4X1,
             'substitution': self.ks3X1
         }])
diff --git a/rsconcept/backend/apps/oss/tests/s_views/t_oss.py b/rsconcept/backend/apps/oss/tests/s_views/t_oss.py
index 6937d9bb..ba52d035 100644
--- a/rsconcept/backend/apps/oss/tests/s_views/t_oss.py
+++ b/rsconcept/backend/apps/oss/tests/s_views/t_oss.py
@@ -55,8 +55,8 @@ class TestOssViewset(EndpointTester):
             alias='3',
             operation_type=OperationType.SYNTHESIS
         )
-        self.owned.set_arguments(self.operation3, [self.operation1, self.operation2])
-        self.owned.set_substitutions(self.operation3, [{
+        self.owned.set_arguments(self.operation3.pk, [self.operation1, self.operation2])
+        self.owned.set_substitutions(self.operation3.pk, [{
             'original': self.ks1X1,
             'substitution': self.ks2X1
         }])
diff --git a/rsconcept/backend/apps/oss/views/oss.py b/rsconcept/backend/apps/oss/views/oss.py
index 6a4a4dc5..a80d8de9 100644
--- a/rsconcept/backend/apps/oss/views/oss.py
+++ b/rsconcept/backend/apps/oss/views/oss.py
@@ -129,7 +129,7 @@ class OssViewSet(viewsets.GenericViewSet, generics.ListAPIView, generics.Retriev
                 oss.create_input(new_operation)
             if new_operation.operation_type != m.OperationType.INPUT and 'arguments' in serializer.validated_data:
                 oss.set_arguments(
-                    operation=new_operation,
+                    target=new_operation.pk,
                     arguments=serializer.validated_data['arguments']
                 )
         return Response(
@@ -305,9 +305,9 @@ class OssViewSet(viewsets.GenericViewSet, generics.ListAPIView, generics.Retriev
                     operation.result.comment = operation.comment
                     operation.result.save()
             if 'arguments' in serializer.validated_data:
-                oss.set_arguments(operation, serializer.validated_data['arguments'])
+                oss.set_arguments(operation.pk, serializer.validated_data['arguments'])
             if 'substitutions' in serializer.validated_data:
-                oss.set_substitutions(operation, serializer.validated_data['substitutions'])
+                oss.set_substitutions(operation.pk, serializer.validated_data['substitutions'])
         return Response(
             status=c.HTTP_200_OK,
             data=s.OperationSchemaSerializer(oss.model).data
diff --git a/rsconcept/backend/apps/rsform/graph.py b/rsconcept/backend/apps/rsform/graph.py
index b6a749ad..bdb6ce6e 100644
--- a/rsconcept/backend/apps/rsform/graph.py
+++ b/rsconcept/backend/apps/rsform/graph.py
@@ -42,6 +42,28 @@ class Graph(Generic[ItemType]):
         if src not in self.inputs[dest]:
             self.inputs[dest].append(src)
 
+    def remove_edge(self, src: ItemType, dest: ItemType):
+        ''' Remove edge from graph. '''
+        if not self.contains(src) or not self.contains(dest):
+            return
+        if dest in self.outputs[src]:
+            self.outputs[src].remove(dest)
+        if src in self.inputs[dest]:
+            self.inputs[dest].remove(src)
+
+    def remove_node(self, target: ItemType):
+        ''' Remove node from graph. '''
+        if not self.contains(target):
+            return
+        del self.outputs[target]
+        del self.inputs[target]
+        for list_out in self.outputs.values():
+            if target in list_out:
+                list_out.remove(target)
+        for list_in in self.inputs.values():
+            if target in list_in:
+                list_in.remove(target)
+
     def expand_inputs(self, origin: Iterable[ItemType]) -> list[ItemType]:
         ''' Expand origin nodes forward through graph edges. '''
         result: list[ItemType] = []
diff --git a/rsconcept/backend/apps/rsform/tests/t_graph.py b/rsconcept/backend/apps/rsform/tests/t_graph.py
index 63713f95..3c99462a 100644
--- a/rsconcept/backend/apps/rsform/tests/t_graph.py
+++ b/rsconcept/backend/apps/rsform/tests/t_graph.py
@@ -26,6 +26,32 @@ class TestGraph(unittest.TestCase):
         self.assertTrue(graph.has_edge(1, 3))
         self.assertTrue(graph.has_edge(2, 1))
 
+    def test_remove_node(self):
+        graph = Graph({
+            1: [2],
+            2: [3, 5],
+            3: [],
+            5: []
+        })
+        self.assertEqual(len(graph.outputs), 4)
+        graph.remove_node(0)
+        graph.remove_node(2)
+        self.assertEqual(graph.outputs[1], [])
+        self.assertEqual(len(graph.outputs), 3)
+
+    def test_remove_edge(self):
+        graph = Graph({
+            1: [2],
+            2: [3, 5],
+            3: [],
+            5: []
+        })
+        graph.remove_edge(0, 1)
+        graph.remove_edge(2, 1)
+        self.assertEqual(graph.outputs[1], [2])
+        graph.remove_edge(1, 2)
+        self.assertEqual(graph.outputs[1], [])
+        graph.remove_edge(1, 2)
 
     def test_expand_outputs(self):
         graph = Graph({