Testing for StructureMap Default Instances

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Have you ever received the good ole “No Default Instance defined for PluginFamily”? error while using StructureMap? I thought I’d share a quick test you can write to catch this error before you deploy the bug. This test is particularly useful when you mostly depend on the default conventions.

In the example provided, I’ll be verifying that I can get a default instance of all my controllers. So I’ve setup 5 controllers and 2 have constructors with some type of dependency.

Something like this:

So now I can setup my test, which looks like this:

If you’re not familiar with TestCaseSource, I blogged about it a few weeks ago on the Headspring blog, so you can read about it there. The test queries the assembly containing HomeController for all types that are a subclass of Controller and are not abstract. After it gets the type, it tries to get an instance of it from the object factory. If it fails, the test fails with what specifically it couldn’t return and which controller couldn’t be instantiated.

Here’s what the test looks like when they all pass:

Here’s what the tests look like when the two with dependencies fails:

Here’s a detailed view of one of the error messages:

Notice it says IAuthenticationService and it failed on the AccountController, so we know exactly where to start looking. The only other thing I probably need to mention is the TestBase, which contains the StructureMap initialization. You could simply register your StructureMap registry file there. Here’s what the example looks like:

If anyone has any suggestions on how to improve the test or if StructureMap already has a test built-in that I’m not familiar with, please share.