Derik Whittaker



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InternalsVisibleTo: Testing internal methods in .Net 2.0

Ok, so maybe I am the last person on the planet to learn about this new attribute, but oh well. 

Last week a co-worker of mine came across this attribute when doing some research and both of us just kinda looked at each other and smiled.  See, for a long while now we have been saying how it would be nice to be able to test non-public methods from external assemblies without the use reflection.  It appears that Microsot thought that this was important enough to add to the framework (thanks guys) in the form of a simple attribute [InternalsVisibleTo] (MSDN Documentation).  Sorry VB.Net developers, Microsoft is again shunning you guys and this attribute is NOT available to you.... :(

In order to use this attribute you need to add one line of code to your AssemblyInfo.cs class for each external assembly that needs to access internal methods.

Now, to create a Simple application to test.  For this example I will create a simple ShoppingCart that takes a Shopping Cart item.

Here is the test that allows the testing of the internal method.

Now, you can test those internal methods from external assemblies.  Like I said above, maybe I was the last to find this, but I am glad I finally did.


Posted 04-09-2007 6:33 AM by Derik Whittaker
Filed under: , ,



Christopher Bennage wrote re: InternalsVisibleTo: Testing internal methods in .Net 2.0
on 04-09-2007 10:28 AM

Nice. I'll confess that I didn't know about the attribute, so maybe I'm the last developer on earth to find out...

Though, there's a lot of arguments going around about marking things internal to begin with.

Derik Whittaker wrote re: InternalsVisibleTo: Testing internal methods in .Net 2.0
on 04-09-2007 10:43 AM


You are correct, there is a lot of arguments about white box vs. black box testing.  It is for that reason I did not even mention that in the post.  

Personally, all i care about is having the tests.  


Ravi Terala wrote re: InternalsVisibleTo: Testing internal methods in .Net 2.0
on 04-09-2007 6:02 PM

Don't use InternalsVisibleTo for testing purposes. Use a wrapper class generated by VS Test Tools. It is a better model and prevents unnecessary exports to test assemblies.

Derik Whittaker wrote re: InternalsVisibleTo: Testing internal methods in .Net 2.0
on 04-09-2007 7:28 PM


Unless they have changed something, the last time i used the wrapper classes i was not very happy.  If i remember correctly I had issues with the wrappers when ever the object that was being wrapped was changed.


jonkas wrote re: InternalsVisibleTo: Testing internal methods in .Net 2.0
on 04-19-2007 11:54 AM

i just ran some quick tests and things work great if the method is marked 'internal' ... how does one go about testing the 'private' and 'protected' access modifiers?

Tor wrote re: InternalsVisibleTo: Testing internal methods in .Net 2.0
on 04-26-2007 8:37 AM

My personal preference is to use this InternalVisibleTo attribute to promote testing rather than the wrapper class generated by VS Test Tools.

I find the concept of wrapper class generation a bit strange and sometimes also problematic. It doesn't work with static classes either

Derik Whittaker wrote Whitebox vs Blackbox testing (location of unit tests)
on 01-28-2008 6:38 AM

Over on the Alt.Net mailing list ( here ) the topic of where to put your unit tests was the hot topic

Direttive al preprocessore | hilpers wrote Direttive al preprocessore | hilpers
on 01-18-2009 8:21 AM

Pingback from  Direttive al preprocessore | hilpers

The Silence Of The LaMs wrote Testowanie jednostkowe metody prywatnej
on 03-14-2010 8:14 PM

Testowanie jednostkowe metody prywatnej

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