System.IO.FileLoadException : Could not load file or assembly 'nunit.framework, Version=2.5.7.10213, Culture=neutral, PublicKeyToken=96d09a1eb7f44a77' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)For further information, use the Exception Details menu item.

It was working fine day before yesterday, and I didn’t modified any system settings, so I didn’t understand what went wrong. Instead of looking into more details, I reinstalled NUnit, but it didn’t worked. Then I tried with NUnit console application, and it was working fine. So I come to know, it was not NUnit problem. Then I tried to diagnose the problem, using Fusion Log Viewer. (FUSLOGVW.exe). From MSDN The Assembly Binding Log Viewer displays details for assembly binds. This information helps you diagnose why the .NET Framework cannot locate an assembly at run time. These failures are usually the result of an assembly deployed to the wrong location, a native image that is no longer valid, or a mismatch in version numbers or cultures. The common language runtime’s failure to locate an assembly typically shows up as a TypeLoadException in your application.You can launch FUSLOGVW.exe, from Visual Studio command prompt, or from Programs > Microsoft Windows SDK v7.1 > Fusion Log Viewer. If your OS is UAC enabled, make sure you are running Fusion Log Viewer as Administrator, otherwise few settings will be disabled. You also need to modify few settings of Fusion Log Viewer for enabling the Assembly binding logging. Click on the settings button, Enable Log all binds to disk and Custom log path, and provide a path in the textbox for storing the log files.

Fusion Log Viewer - Settings

After launching Fusion Log Viewer run the application to reproduce the issue.

Fusion Log Viewer - All binding details

After you getting the error, click Refresh button of Fusion Log Viewer, it will display binding details in the list view and you can double click on each item and find the exact issue. In my scenario, I some how copied some old NUnit Framework assembly to the location of test assembly, and NUnit GUI application was trying to load that assembly instead of the valid one. I removed the assembly and it started working fine.

The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command-line sxstrace.exe tool for more detail.

So I thought of work around this issue. To reproduce the issue, I tampered the exe.config file of one of my application, by removing <configuration> tag from the file. And it started throwing the exception.

The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command-line sxstrace.exe tool for more detail.

I verified the same with EventViewer, and I found a message like this, under Windows Logs > Application

Activation context generation failed for “C:\CaptureItPlus\Binaries\CaptureItPlus.exe”. Error in manifest or policy file “C:\CaptureItPlus\Binaries\CaptureItPlus.exe.Config” on line 1. Invalid Xml syntax.

The error message is pretty self explanatory. If you are not able to access the event viewer, the other option is using sxstrace.exe tool. You can enable run the sxstrace in trace mode, you can do this by following command.

sxstrace.exe Trace -logfile:C:\captureittrace.log

And execute the application. After getting exception, stop the tracing and you can parse the log file using following command.

sxstrace.exe Parse -logfile:C:\captureittrace.log -outfile:C:\captureittrace.txt

It is required because .log is a binary file. Now open the .txt file, you can see similar message,

INFO: Parsing Application Config File C:\CaptureItPlus\Binaries\CaptureItPlus.exe.Config.
ERROR: Line 1: XML Syntax error.
ERROR: Activation Context generation failed.
End Activation Context Generation.

Now open the .exe.config and add the missing , now double click on the application, this issue will be resolved.

The breakpoint will not currently be hit. No symbols have been loaded for this document

This issues is because of NUnit loads up in .Net 2.0 and then has to load up the modules in 4.0, so does so under the agent process. The solutionis to force NUnit to run under .Net 4.0. This will can done by modifing the NUnit.exe.config file.

<startup>
	<requiredRuntime version="v4.0.30319" />
</startup>

This will fix the issue, also you are able to debug with breakpoints. If you are running Windows 7, make sure you are opening the NUnit.exe.config file as Administrator. And if your OS is 64 bit, you should modify nunit-x86.exe.config file.

Happy Unit testing

Advanced Properties

But this option will not work, when you are opening a project or solution by double clicking on the solution file. Here is the tip which will help you to open Visual Studio files with Administrator option. All the solution files are opening using a small utility called VSLauncher.exe, which can be found in C:\Program Files (x86)\Common Files\microsoft shared\MSEnv folder. Right click on the executable, select Properties and select the Compatibility tab, Check the Run this program as an Administrator, under Privilege level. Apply the settings and click OK. Now open any solution, Windows will show the UAC dialog.

VSLauncher.exe Properties