Fix NUNIT Run

appveyor.yml

@@ -16,9 +16,8 @@ build:
 after_build:
   - ps: .\nuget\pack.ps1
 
-test:
-  assemblies:
-    - WpfDesign.Designer\Tests\obj\Debug\ICSharpCode.WpfDesign.Tests.dll
+test_script:
+  nunit-console WpfDesign.Designer\Tests\obj\Debug\ICSharpCode.WpfDesign.Tests.dll /framework:net-4.5
 
 artifacts:
   - path: XamlDesigner\bin\Debug\ICSharpCode.WpfDesign.Designer.dll