How can I unit test a Windows Service?

Question

.NET Framework: 2.0 Preferred Language: C#

I am new to TDD (Test Driven Development).

First of all, is it even possible to unit test Windows Service?

Windows service class is derived from ServiceBase, which has overridable methods,

1. OnStart
2. OnStop

How can I trigger those methods to be called as if unit test is an actual service that calls those methods in proper order?

At this point, am I even doing a Unit testing? or an Integration test?

I have looked at WCF service question but it didn't make any sense to me since I have never dealt with WCF service.

Answer 1

I'd probably recommend designing your app so the "OnStart" and "OnStop" overrides in the Windows Service just call methods on a class library assembly. That way you can automate unit tests against the class library methods, and the design also abstracts your business logic from the implementation of a Windows Service.

In this scenario, testing the "OnStart" and "OnStop" methods themselves in a Windows Service context would then be an integration test, not something you would automate.

Answer 2

I have unit tested windows services by not testing the service directly, but rather testing what the service does.

Typically I create one assembly for the service and another for what the service does. Then I write unit tests against the second assembly.

The nice thing about this approach is that your service is very thin. Basically all it does is call methods to do the right work at the right time. Your other assembly contains all the meat of the work your service intends to do. This makes it very easy to test and easy to reuse or modify as needed.