test properties (#107)

* test `functools.cached_property`

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_edgecases.py

@@ -1,3 +1,7 @@
+import functools
+
+import pytest
+
 import znflow
 
 
@@ -12,6 +16,13 @@ def result(self):
         raise TypeError("This value is not available until the node is run.")
 
 
+class NodeCachedProperty(znflow.Node):
+
+    @functools.cached_property
+    def result(self):
+        raise TypeError("This value is not available until the node is run.")
+
+
 class ConnectResults(znflow.Node):
     @property
     def result(self):
@@ -33,6 +44,20 @@ def test_PlainNode():
 
     assert isinstance(con, znflow.Connection)
 
+    with pytest.raises(TypeError):
+        con.result
+
+
+def test_NodeCachedProperty():
+    with znflow.DiGraph():
+        node1 = NodeCachedProperty()
+        con = node1.result
+
+    assert isinstance(con, znflow.Connection)
+
+    with pytest.raises(TypeError):
+        con.result
+
 
 def test_ConnectResults():
     with znflow.DiGraph() as graph: