Resolve "Replacing Operations in SFG"

I added some thoughts on how this issue was implemented in #15 (closed), for most part on how we handle replacing several operations. Closes #15 (closed)

test/test_signal_flow_graph.py

@@ -170,25 +170,19 @@ class TestReplaceComponents:
 
     def test_replace_addition_large_tree(self, large_operation_tree):
         sfg = SFG(outputs=[Output(large_operation_tree)])
-        component_id = "add2"
+        component_id = "add3"
 
         sfg = sfg.replace_component(Multiplication(name="Multi"), _id=component_id)
         assert "Multi" in sfg._components_by_name.keys()
+        assert component_id not in sfg._components_by_id.keys()
     
     def test_replace_no_input_component(self, operation_tree):
         sfg = SFG(outputs=[Output(operation_tree)])
         component_id = "c1"
-        _value = sfg.find_by_id(component_id).value
+        _const = sfg.find_by_id(component_id)
         
-        sfg = sfg.replace_component(Constant(10), _id=component_id)
-        assert _value != sfg.find_by_id(component_id).value
-
-    def test_replace_no_destination_component(self, operation_tree):
-        sfg = SFG(outputs=[Output(operation_tree)])
-        component_id = "add1"
-
-        sfg = sfg.replace_component(Multiplication(name="Multi"), _id=component_id)
-        assert "Multi" in sfg._components_by_name.keys()
+        sfg = sfg.replace_component(Constant(1), _id=component_id)
+        assert _const is not sfg.find_by_id(component_id)
 
     def test_no_match_on_replace(self, large_operation_tree):
         sfg = SFG(outputs=[Output(large_operation_tree)])