Add tests for the misc.cachedproperty descriptor

Add a few tests that verify it is working as expected.

Change-Id: I6c062f84f7c2a6baf8fc9a697ebe2d715f82d332

taskflow/tests/unit/test_utils.py

@@ -312,6 +312,65 @@ class GetAllClassNamesTest(test.TestCase):
         self.assertEqual(names, test_utils.RUNTIME_ERROR_CLASSES[:-2])
 
 
+class CachedPropertyTest(test.TestCase):
+    def test_attribute_caching(self):
+
+        class A(object):
+            def __init__(self):
+                self.call_counter = 0
+
+            @misc.cachedproperty
+            def b(self):
+                self.call_counter += 1
+                return 'b'
+
+        a = A()
+        self.assertEqual('b', a.b)
+        self.assertEqual('b', a.b)
+        self.assertEqual(1, a.call_counter)
+
+    def test_custom_property(self):
+
+        class A(object):
+            @misc.cachedproperty('_c')
+            def b(self):
+                return 'b'
+
+        a = A()
+        self.assertEqual('b', a.b)
+        self.assertEqual('b', a._c)
+
+    def test_no_delete(self):
+
+        def try_del(a):
+            del a.b
+
+        class A(object):
+            @misc.cachedproperty
+            def b(self):
+                return 'b'
+
+        a = A()
+        self.assertEqual('b', a.b)
+        self.assertRaises(AttributeError, try_del, a)
+        self.assertEqual('b', a.b)
+
+    def test_set(self):
+
+        def try_set(a):
+            a.b = 'c'
+
+        class A(object):
+            @misc.cachedproperty
+            def b(self):
+                return 'b'
+
+        a = A()
+        self.assertEqual('b', a.b)
+        self.assertRaises(AttributeError, try_set, a)
+        self.assertEqual('b', a.b)
+
+
 class AttrDictTest(test.TestCase):
     def test_ok_create(self):
         attrs = {