Question: I don't know how to specify correct mask to search for my test assemblies in TFS2010 build definition.
I'm not using default Binaries folder for output assemblies. Each test project has its own bin\Debug or bin\Release output folder.
If I use the default mask \*\*\\*test\*.dll my tests failed with this error:

```
API restriction: The assembly 'file:///E:\Builds\....\obj\Debug\xxx.IntegrationTests.dll' 
has already loaded from a different location. It cannot be loaded from a new location within the same appdomain.

```

This is because \*\*\\*test\*.dll mask will find multiple results for the same assembly in the bin\Debug and obj\Debug folders. 

I tried to change this mask to exclude obj\Debug folder and use bin only:

```
**\bin\Debug\*test*.dll
**\bin\**\*test*.dll
**\Debug\*test*.dll

```

but FindMatchingFiles activity return always 0 results. 

It is working only when I pass full path to the test assembly. 

What is the correct mask if I want to exclude obj\Debug folders from test assembly search?

**WORKAROUND**:  

I'm still using FindMatchingFiles activity, but I had to add Assign activity with following params:  

```
To - testAssemblies
From - testAssemblies.Where(Function(o) Not o.Contains("\obj\")).ToList()

```

I'm filtering all test assemblies found in the "obj" folders this way.

Answer: 
The build activity that is of interest to you is named "Find Test Assemblies":
![enter image description here](https://i.stack.imgur.com/O8nh4.png)

So, what you place at the build definition is concatenated after build script variable `outputDirectory`.

This `outputDirectory` is initialized for each configuration in activity "Initialize OutputDirectory":
![enter image description here](https://i.stack.imgur.com/fzLZU.png)

You can queue a new build where you set your 'Logging Verbosity' equal to `Diagnostic`. Once this has ran (and failed), check for what is going on with your build. 

My guess is that you have issues with your configuration/platform settings, but without concrete input that's just guessing.
I ran into this issue but found that rather than just bin and obj containing duplicates, I had many copies of the same DLLs appearing in various project folders.

Ludwo's answer with `Assign` was nearly enough to fix it, but for my situation I needed a more general value for the `From` parameter. This VB groups the discovered file paths by file name, and then picks the first path from each group. It of course will only work if and only if each file name maps to one logical DLL:

```
testAssemblies.GroupBy(Function(a) New System.IO.FileInfo(a).Name).[Select](Function(g) g.First())

```