def setUp(self): reg = registry_tests.small_testing_registry() scheme = Scheme() zero = scheme.new_node(reg.widget("zero")) one = scheme.new_node(reg.widget("one")) add = scheme.new_node(reg.widget("add")) scheme.new_link(zero, "value", add, "left") scheme.new_link(one, "value", add, "right") self.scheme = scheme