Operation Tree Traversing

Reformatted the tests, the tests might need to be changed if signal is changed though. Closes #11 (closed)

test/fixtures/operation_tree.py

@@ -46,4 +46,13 @@ def addition_tree():
     add_oper = Addition()
     create_operation(Constant, add_oper, 0, value=2)
     create_operation(Constant, add_oper, 1, value=3)
-    return add_oper
\ No newline at end of file
+    return add_oper
+
+@pytest.fixture
+def looping_addition_tree(addition_tree):
+    add_oper_signal_source = SignalSource(addition_tree, 0)
+    add_oper_signal_dest = SignalDestination(addition_tree, 0)
+    add_oper_signal = Signal(add_oper_signal_source, add_oper_signal_dest)
+    addition_tree._output_ports[0].connect(add_oper_signal)
+    addition_tree._input_ports[0].connect(add_oper_signal)
+    return addition_tree
\ No newline at end of file