implement config layering

test/property/test_property_layer.py

@@ -4,6 +4,15 @@ from unittest.mock import Mock
 
 
 class PropertyLayerTest(TestCase):
+    def testCreationWithKwArgs(self):
+        pm = PropertyLayer(testkey="value")
+        self.assertEqual(pm["testkey"], "value")
+
+        # this should be synonymous, so this is rather for illustration purposes
+        contents = {"testkey": "value"}
+        pm = PropertyLayer(**contents)
+        self.assertEqual(pm["testkey"], "value")
+
     def testKeyIsset(self):
         pm = PropertyLayer()
         self.assertFalse("some_key" in pm)

test/property/test_property_stack.py

@@ -185,3 +185,13 @@ class PropertyStackTest(TestCase):
 
         stack.replaceLayer(0, second_layer)
         mock.method.assert_not_called()
+
+    def testWritesToExpectedLayer(self):
+        om = PropertyStack()
+        low_pm = PropertyLayer()
+        high_pm = PropertyLayer()
+        low_pm["testkey"] = "low value"
+        om.addLayer(1, low_pm)
+        om.addLayer(0, high_pm)
+        om["testkey"] = "new value"
+        self.assertEqual(low_pm["testkey"], "new value")