My team and I have spotted some odd behaviour with the latest version of JustMock (2015.3.929.5) when targeting a Windows Store app. If we create a mock for an object in a helper method, the mock fails when making assertions for calls to the mock. The following code illustrates the issue: [TestMethod] public void ThisWillFail() { var subject = CreateSubject(); subject.DoSomething(); subject.Assert(s => s.DoSomething(), Occurs.Once()); } [TestMethod] public void ThisWillPass() { var subject = Mock.Create<ISubject>(); subject.DoSomething(); subject.Assert(s => s.DoSomething(), Occurs.Once()); } public interface ISubject { void DoSomething(); } private static ISubject CreateSubject() { return Mock.Create<ISubject>(); } In this code, the first test will fail but the second test will pass. The only difference is that, in the first test, we're setting up the mock in a helper method. We have a "Unit Test Library (.NET for Windows Store apps)" referencing the Telerik.JustMock assembly. I have attached a simple project containing this implementation. It's worth noting that the same code passes in a regular .NET class library; it only fails in a "Unit Test Library (.NET for Windows Store apps)". It's also worth noting that this worked under an older version of the assembly (2014.3.1021.2). Any help would be appreciated, as we currently have around 3,000 tests and a good proportion of them set up their mocks using a helper method in this way. Regards William Cowell