public void ShouldAttachNewRegionByUsingRegisteredRegionAdapterMappings() { var mappings = new RegionAdapterMappings(); var mockRegionAdapter = new MockRegionAdapter(); mappings.RegisterMapping(typeof(DependencyObject), mockRegionAdapter); var regionManager = new RegionManager(mappings); var control = new ContentControl(); regionManager.AttachNewRegion(control, "TestRegionName"); Assert.IsTrue(mockRegionAdapter.InitializeCalled); Assert.AreEqual(control, mockRegionAdapter.InitializeArgument); }