Determine if code is running as part of a unit test

Question

I have a unit test (nUnit). Many layers down the call stack a method will fail if it is running via a unit test.

Ideally you would use something like mocking to setup the object that this method is depending on but this is 3rd party code and I can't do that without a lot of work.

I don't want setup nUnit specific methods - there are too many levels here and its a poor way of doing unit test.

Instead what I would like to do is to add something like this deep down in the call stack

#IF DEBUG // Unit tests only included in debug build
if (IsRunningInUnitTest)
   {
   // Do some setup to avoid error
   }
#endif

So any ideas about how to write IsRunningInUnitTest?

P.S. I am fully aware that this is not great design, but I think its better than the alternatives.

Answer 1

I've done this before - I had to hold my nose while I did it, but I did it. Pragmatism beats dogmatism every time. Of course, if there is a nice way you can refactor to avoid it, that would be great.

Basically I had a "UnitTestDetector" class which checked whether the NUnit framework assembly was loaded in the current AppDomain. It only needed to do this once, then cache the result. Ugly, but simple and effective.

Answer 2

Taking Jon's idea this is what I came up with -

using System;
using System.Reflection;

/// <summary>
/// Detect if we are running as part of a nUnit unit test.
/// This is DIRTY and should only be used if absolutely necessary 
/// as its usually a sign of bad design.
/// </summary>    
static class UnitTestDetector
{

    private static bool _runningFromNUnit = false;      

    static UnitTestDetector()
    {
        foreach (Assembly assem in AppDomain.CurrentDomain.GetAssemblies())
        {
            // Can't do something like this as it will load the nUnit assembly
            // if (assem == typeof(NUnit.Framework.Assert))

            if (assem.FullName.ToLowerInvariant().StartsWith("nunit.framework"))
            {
                _runningFromNUnit = true;
                break;
            }
        }
    }

    static bool IsRunningFromNunit
    {
        get { return _runningFromNUnit; }
    }
}

Pipe down at the back we're all big enough boys to recognise when we're doing something we probably shouldn't ;)

Answer 3

Adapted from Ryan's answer. This one is for the MS unit test framework.

The reason I need this is because I show a MessageBox on errors. But my unit tests also test the error handling code, and I don't want a MessageBox to pop up when running unit tests.

/// <summary>
/// Detects if we are running inside a unit test.
/// </summary>
public static class UnitTestDetector
{
    static UnitTestDetector()
    {
        string testAssemblyName = "Microsoft.VisualStudio.QualityTools.UnitTestFramework";
        UnitTestDetector.IsInUnitTest = AppDomain.CurrentDomain.GetAssemblies()
            .Any(a => a.FullName.StartsWith(testAssemblyName));
    }

    public static bool IsInUnitTest { get; private set; }
}

And here's a unit test for it:

    [TestMethod]
    public void IsInUnitTest()
    {
        Assert.IsTrue(UnitTestDetector.IsInUnitTest, 
            "Should detect that we are running inside a unit test."); // lol
    }