Today has been a bang my head on the keyboard type of morning. This morning I set out to write tests to make sure the actions inside of our project are audited correctly by sending messages to a message queue. Now as a good developer we don't want to test the action of sending to the message queue but just that the message was sent to the method on the ILog interface. This seemed simple enough so let's get started.

Our audit service uses something similar to this.Log() which has some static methods to retrieve the correct logger for the type. We have this abstracted away in a static container [I know not ideal, but what we have so far] so we can swap it out easily for unit tests to use a NullLog or in this case a TestableLogger

I started out with the following logic

var testableLogger = new TestableLogger();
Log.Container = new UnityContainer().RegisterInstance<ILog>(testableLogger);

Everything worked perfectly and my Assert was happy

GenericAuditMessage genericAuditMessage = testableLogger.AuditMessages.Cast<GenericAuditMessage>().FirstOrDefault();
Assert.IsNotNull(genericAuditMessage);

Feeling a slight moment of happiness I went onto my next test and that one failed and now my first test that passed failed again.

What is going on?

I figured it had to be something with the static variable so off to google I went to get some answers. The first thing I saw that was promising was this answer on stack overflow. From that I tried to use the debug with an existing task process which showed me that at one point the list had 3 items but in the assert it was 0. There has to be a way to isolate these tests.

Isolated Attribute

Well that was simple enough, add the isolated attribute to your test.

        [TestMethod]
        [Isolated]

After I added this to the offending tests everything was green again.

Conclusion

This problem resulted from the design of the application (which is on my mental to do list), but if you ever run into a problem with a static variable and NCrunch give the [Isolated] attribute a try.