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Wednesday
Nov242010

Extending the Gallio Automation Platform

I’ve been doing a lot recently with Gallio, and I have to say I like it. Gallio is an open source project that bills itself as an automation framework, but its most compelling use by far is as a unit testing platform. It supports every unit test framework that I’ve ever heard of (including the test framework that spawned it, MbUnit, which is now another extension to Gallio), and has great tooling hooks for the flexibility to run tests from many different environments.

Gallio came onto my radar when my company had to choose whether to enhance or replace an in-house testing platform which was written back in the days when the unit testing tools available were not all that sophisticated. The application had evolved to become quite feature-rich, but the user interfaces (a Windows Forms application and a console variant), needed a makeover, and there were two schools of thought: invest resources in further enhancing and maintaining an internal tool, or revisit the current external options available to us.

We use NHibernate as a persistence layer, and have been able to benefit greatly from taking advantage of the improvements made to that open-source product, so I was keen to see if we could lean on the wider community again for our new unit testing framework.

I’d had a fair amount of experience with MSTest in a former life, but quickly dismissed it as an option when comparing it against the feature sets available in the latest versions of NUnit and MbUnit. Our in-house framework was clearly influenced by an early version of NUnit, and made significant use of parameterized tests, many of which were quite complex. It seemed that data-driven testing in MSTest hadn’t really progressed beyond the ADO.NET DataSource, whereas frameworks like MbUnit have started to provide quite powerful, generative capabilities for parameterizing test fixtures and test cases.

So one option on the table was to port (standardize, in reality) all of our existing tests to NUnit or MbUnit tests. This would allow us to run the tests in a number of ways, instead of just via the two tools we had built around our own framework. With my developer hat on, I really like the ability to run one or more tests directly from Visual Studio in ReSharper, and for the buildmaster in me, running and tracking those same tests from a continuous integration server like TeamCity is also important. We had neither of these capabilities with our existing platform.

Another factor in our deliberations became the feature set of the UI for our in-house tool. We had some feature requirements here that we would have to take with us going forward, so if we weren’t going to continue to maintain ours, we needed to find a replacement test runner UI that could be extended.

Enter Icarus, which itself is another extension to Gallio that provides a great Windows Forms UI that, all by itself, does everything you might need a standard test runner application to do, but that’s only the beginning. Adding your own functionality to the UI is actually quite easy to achieve. I was able to add an entire test pane with just a handful of source files and few dozen lines of code, and we were up and running with a couple of core features we needed from our new test runner (and this was an ElementHost-ed WPF panel, at that).

And that’s not the end of the story. Even if we wanted to use Gallio/Icarus going forward, we were still faced with the prospect of porting all of our existing unit tests to one of the many supported by Gallio (with NUnit and MbUnit being the two favourites). We really didn’t want to do this, and would probably have lived with a bifurcated testing architecture where the existing tests would have stayed with our internal framework and any new tests would be built for NUnit or MbUnit. This would have been less that ideal, but it probably would still have been worthwhile in order to avoid maintaining our own tools while watching the third party tools advance without us.

As it turns out, we didn’t need to make that choice, because adding a whole new test runner framework to Gallio is as easy as extending the Icarus UI. By shamelessly cribbing from the existing Gallio adapters for NUnit and MbUnit, we were able to reuse significant parts of our in-house framework, build a new custom adapter around those, and run all of our existing unit tests alongside new NUnit tests in both the Icarus UI and the Gallio Echo command-line test runners. As an added bonus, since Gallio is also supported by ReSharper, we were now able to run our old tests directly from within Visual Studio, for free, something we had not been able to do with our platform. It took about two days to complete all of the custom adapter work.

I’m quite optimistic that we’ll be able to really enhance our unit testing practices by leveraging Gallio, and without the effort it would take to maintain a lot of complex internal code. The extensibility of Gallio and Icarus is really quite phenomenal – kudos to all those responsible.

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