public void CalculateNewValueTest() { // Arrange. var fileValue = Mock.Create<IFileProcess>(); var updater = new FileFieldUpdater { ValueCalculator = (s, d) => fileValue }; // Act. updater.CalculateNewValue(new DataTriggerSourceData(), Mock.Create<IEditableRoot>()); // Assert. Assert.AreSame(fileValue, updater.NewValue); // Arrange. updater.ValueCalculator = (s, d) => "Invalid"; // Act / Assert. TestsHelper.VerifyThrow<InvalidOperationException>(() => updater.CalculateNewValue(new DataTriggerSourceData(), Mock.Create<IEditableRoot>())); }