Hudson : warning MSB3245: Could not locate the assembly "nunit.framework"

The issue isn't the nunit-console.exe (or whatever the name).

The issue is that you cannot find nunit.framework.dll...as a reference in your project file (.csproj for C#).

Your unit-test project, you need to open it and find how/where the reference to the nunit.framwork.dll is wired.

Post the .csproj code if that is confusing.

EDIT:

<HintPath>Dll\nunit.framework.dll</HintPath>

The issue is that you need to "download" or copy or svn-export or svn-checkout or nuget-get that file. And place it in the relative directory to your .csproj.

Because you have specified a HintPath, it will NOT find the one in this below directory:

C:\Program Files (x86)\NUnit 2.X.Y\bin\nunit.framework.dll

Basically, the HintPath says "I expect to find this file HERE", and your MSBUILD error says "I did not find it where the HintPath said it would be."