Derik Whittaker



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Testing your IoC Bindings

One thing I like to do when I am using a IoC (Inversion of Control) container is to create simple test that ensure that my objects have been wired up correctly and can be created via the IoC container. 

I know this may seem like overkill, but I feel that by having my IoC bindings covered by tests I am covering all my bases.

So, what does testing my bindings do for me

  • Allows me to know if my object is configured correctly
    By having these tests I will know immediately if I have somehow broken my IoC bindings glue (yes, glue is the technical term in this case). 

    It is not hard to phantom that when making changes to your IoC bindings logic (either via config files or via inline code) you can mistakenly break something.  Having these tests provides me immediate feedback if this were to happen.
  • Allows me to know if my objects dependencies are configured correctly
    Setting up the wiring for your main object is only half the battle.  When using an IoC container many time you are going to have that container do some sort of Constructor Injection of your dependencies. 

    By having tests that simply create my object with IoC I will find out immediately if one of my dependency objects is not wired up.  This scenario is pretty common and having this test can save you some headaches.

Here is the test code I use for my IoC bindings tests:

public void CanCreateViaDI()
    var iocObject = ObjectFactory.GetInstance< YourObjectHere >();
    Assert.That( iocObject, Is.Not.Null );


Hope this helps someone.

Till next time,

[----- Remember to check out DimeCasts.Net -----]

Posted 09-10-2008 6:53 AM by Derik Whittaker



Dew Drop - September 10, 2008 | Alvin Ashcraft's Morning Dew wrote Dew Drop - September 10, 2008 | Alvin Ashcraft's Morning Dew
on 09-10-2008 9:12 AM

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Scott Parker wrote re: Testing your IoC Bindings
on 09-10-2008 10:23 AM

Does StructureMap actually return null like that? My experience when I've screwed up my bindings is that I've gotten an exception at some point.

Of course, now that I think about it, usually my mismatches have been related to public classes relying on internal components in their constructors, which generates a framework exception, not a StructureMap exception.

Anyway, good thoughts. Looking forward to see what jdn has to say on the subject as well.


Jeremy D. Miller wrote re: Testing your IoC Bindings
on 09-10-2008 10:56 AM

StructureMap will blow up with StructureMapException if it doesn't know what to do with "YourObjectHere"


If all you want is a quck sanity check, and you're using 2.5, do:

// set up the container


and that will find all missing ctor values, properties, try to build everything it knows about, and run all environment tests

Derik Whittaker wrote re: Testing your IoC Bindings
on 09-10-2008 10:58 AM


Yea i know it will throw an exception for some reason i still feel better having that assert.

However, i did not know there was the AssertConfigurationIsValid or did not pay any attention.  I will use that going forward.


Matt Hinze wrote re: Testing your IoC Bindings
on 09-10-2008 12:02 PM

Yikes.  That is good to know, Jeremy.  This is actually a desirable test though.  We have a ton of controllers and subcontrollers and to assert that they are registered in the container is a good fast fail before we get a YSOD.  I will request this feature...

2008 September 11 - Links for today « My (almost) Daily Links wrote 2008 September 11 - Links for today &laquo; My (almost) Daily Links
on 09-11-2008 1:02 AM

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computer network consulting wrote re: Testing your IoC Bindings
on 08-03-2009 1:26 AM

Thanks for sharing very useful information as well as nice blog.

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