Integration Testing with FubuMVC and OWIN

tl;dr: Having an OWIN host to run FubuMVC applications in process made it much easier to write integration tests and I think OWIN will end up being a very positive thing for the .Net development community.

FubuMVC is still dead-ish as an active OSS project, but the things we did might still be useful to other folks so I’m continuing my series of FubuMVC lessons learned retrospectives — and besides, I’ve needed to walk a couple other developers through writing integration tests against FubuMVC applications in the past week so writing this post is clearly worth my time right now.

One of the primary design goals of FubuMVC was testability of application code, and while I think we succeeded in terms of simpler, cleaner unit tests from the very beginning (especially compared to other web frameworks in .Net), there are so many things that can only be usefully tested and verified by integration tests that execute the entire HTTP stack.

Quite admittedly, FubuMVC was initially very weak in this area — partially because the framework itself only ran on top of ASP.Net hosting. While we had good unit test coverage from day one, our integration testing story had to evolve as we went in roughly these steps:

  1. Haphazardly build sample usages of features in an ASP.Net application that had to run hosted in either IIS or IISExpress that had to be executed manually. Obviously not a great solution for regression testing or for setting up test scenarios either.
  2. A not completely successful attempt to run FubuMVC on the early “Delegate of Doom” version of the OWIN specification and the old Kayak HTTP server. It worked just well enough to get my hopes up but didn’t really fly (there were some scenarios where it would just hang). If you follow me on Twitter and seen me blast OWIN as a “mystery meat” API, it’s largely because of lingering negativity from our first attempt.
  3. Running FubuMVC on top of Web API’s Self Host libraries. This was a nice win as it enabled us to embed FubuMVC applications in process for the first time, and our integration test coverage improved quickly. The Self Host option was noticeably slow and never worked on Mono* for us.
  4. Just in time for the 1.0 release, we finally made a successful attempt at OWIN hosting with the less insane OWIN 1.0 specification, and we’ve ran most of our integration tests and acceptance tests on Katana ever since. Moving to Katana and OWIN was much faster than the Web API Self Host infrastructure and at least in early versions, worked on Mono (the Katana team has periodically broken Mono support in later versions).
  5. For the forthcoming 2.0 release I built a new “InMemoryHost” model that can execute a single HTTP request at a time using our OWIN support without needing any kind of HTTP server.

I cannot overstate how valuable it has been to have an embedded hosting model has been for automated testing. Debugging test failures, using the application services exactly as the real application is configured, and setting up test data in databases or injecting in fake services is much easier with the embedded hosting models.

Here’s a real problem that I hit early this year. FubuMVC’s content negotiation (conneg) logic for selecting readers and writers was originally based only on the HTTP accepts and content-type headers, which is great and all except for how many ill behaved clients there are out there that don’t play nice with the HTTP specification. I finally went into our conneg support earlier this year and added support for overriding the accepts header, with an in the box default that looked for a query string on the request like “?format=json” or “format=xml.” While there are some unit tests for the internals of this feature, this is exactly the kind of feature that really has to be tested through an entire HTTP request and response to verify correctness.

If you’re having any issues with the formatting of the code samples, you can find the real code on GitHub at the bottom of this page.


I started by building a simple GET action that returned a simple payload:

    public class OverriddenConnegEndpoint
        public OverriddenResponse get_conneg_override_Name(OverriddenResponse response)
            return response;

    public class OverriddenResponse
        public string Name { get; set; }

Out of the box, the new “conneg/override/{Name}” route up above would respond with either a json or xml serialization of the output model based on the value of the accepts header, with “application/json” being the default representation in the case of wild cards for the accepts header. In the functionality, content negotiation needs to also look out for the new query string rules.

The next step is to define our FubuMVC application with a simple IApplicationSource class in the same assembly:

    public class SampleApplication : IApplicationSource
        public FubuApplication BuildApplication()
            return FubuApplication.DefaultPolicies().StructureMap();

The role of the IApplicationSource class in a FubuMVC application is to bootstrap the IoC container for the application and define any custom policies or configuration of a FubuMVC application. By using an IApplicationSource class, you’re establishing a reusable configuration that can be quickly applied to automated tests to make your tests as close to the production deployment of your application as possible for more realistic testing. This is crucial for FubuMVC subsystems like validation or authorization that mix in behavior to routes and endpoints off of conventions determined by type scanning or configured policies.


Using Katana and EndpointDriver with FubuMVC 1.0+

First up, let’s write a simple NUnit test for overriding the conneg behavior with the new “?format=json” trick, but with Katana and the FubuMVC 1.0 era EndpointDriver object:

        public void with_Katana_and_EndpointDriver()
            using (var server = EmbeddedFubuMvcServer
                server.Endpoints.Get("conneg/override/Foo?format=json", acceptType: "text/html")

Behind the scenes, the EmbeddedFubuMvcServer class spins up the application and a new instance of a Katana server to host it. The “Endpoints” object exposes a fluent interface to define and execute an HTTP request that will be executed with .Net’s built in WebClient object. The EndpointDriver fluent interface was originally built specifically to test the conneg support in the FubuMVC codebase itself, but is usable in a more general way for testing your own application code written on top of FubuMVC.


Using the InMemoryHost and Scenarios in FubuMVC 2.0

EndpointDriver was somewhat limited in its coverage of common HTTP usage, so I hoped to completely replace it in FubuMVC 2.0 with a new “scenario” model somewhat based on the Play Framework’s Play Specification tooling in Scala. I knew that I also wanted a purely in memory hosting model for integration tests to avoid the extra time it takes to spin up an instance of Katana and sidestep potential port contention issues.

The result is the same test as above, but written in the new “Scenario” style concept:

        public void with_in_memory_host()
            // The 'Scenario' testing API was not completed,
            // so I never got around to creating more convenience
            // methods for common things like deserializing JSON
            // into .Net objects from the response body
            using (var host = InMemoryHost.For<SampleApplication>())
                host.Scenario(_ => {



The newer Scenario concept was an attempt to make HTTP centric testing be more declarative. C# is not as expressive as Scala is, but I was still trying to make the test expression as clean and readable as possible and the syntax above probably would have evolved after more usage. The newer Scenario concept also has complete access to FubuMVC 2.0’s raw HTTP abstractions so that you’re not limited at all in what kinds of things you can express in the integration tests.

If you want to see more examples of both EmbeddedFubuMvcServer/EndpointServer and InMemoryHost/Scenario in action, please see the FubuMVC.IntegrationTesting project on GitHub.


Last Thoughts

If you choose to use either of these tools in your own FubuMVC application testing, I’d highly recommend doing something at the testing assembly level to cache the InMemoryHost or EmbeddedFubuMvcServer so that they can be used across test fixtures to avoid the nontrivial cost of repeatedly initializing your application.

While I’m focusing on HTTP centric testing here, using either tool above also has the advantage of building your application’s IoC container out exactly the way it should be in production for more accurate integration testing of underlying application services.


If I had to do it all over again…

We would have had an embedded hosting model from the very beginning, even if it had been on a fake, “only one HTTP request at a time” model. Moreover, if we were to ever reboot a new FubuMVC like web framework in the future KVM, I would vote for wrapping any new framework completely around the OWIN signature as our one and only model of an HTTP request. In any theoretical future effort, I’d invest time from the very beginning in something like FubuMVC 2.0’s InMemoryHost model early to make integration and acceptance testing easier and faster.

With the recent release of StructureMap 3, I’d also opt for a new child container model such that you can fake out application services on a test by test basis and rollback to the previous container state without having to re-initialize the entire application each time for faster testing.


* Mono support was a massive time sink for the FubuMVC project and never really paid off. Maybe having Xamarin involved much earlier in the new KVM .Net runtime and the emphasis on PCL supportwill make that situation much better in the future.

2 thoughts on “Integration Testing with FubuMVC and OWIN

  1. Pingback: The Morning Brew - Chris Alcock » The Morning Brew #1665

  2. Pingback: Dew Drop – August 4, 2014 (#1828) | Morning Dew

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