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Adds BDD .Should() assertion syntax to NUnit
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Yet another library that adds BDD-style Should() assertions to NUnit.

It's done using a whole 16 lines of code plus some optional Should*() helper methods.


Install-Package NUnit.Should


Latest version:

Download .dll for .NET 2.0 or .NET 3.0+

Browse Source


I like NUnit. When I started doing .NET development back in 2005, it was the conventional testing library. Although Visual Studio now comes with MSTest, I've found that NUnit still seems to be the conventional testing library for open-source projects.

I have a problem with NUnit, however. For the past 3-4 years, I've been writing assertions like this using RSpec:

the_number.should == 5
the_dogs.should include('rover')

I love the RSpec syntax for making assertions. It's very natural.

In NUnit, there are 2 different styles that I could use to write similar assertions:

Assert.AreEqual(5, theNumber);
Assert.Contains("rover", theDogs);

Or you can use Assert.That:

Assert.That(theNumber, Is.EqualTo(5));
Assert.That(theDogs, Contains.Item("rover"));

That's not too bad, right?

Well, when I recently started doing C# full-time again, I didn't mind using Assert.Whatever(expected, actual) or the Assert.That syntax (which reads better, but is very verbose).

But then I remembered that the language you use to write your specs is actually important! There's a reason why BDD frameworks use Should instead of Assert, even though they do the same things.

When you say something.Should(be in some state) you're more likely to check for an object's behaviors/states, in my honest opinion. When you Assert.AreEqual(foo, bar) you're more likely to be writing low level "unit tests."

It's just different wording. But it's important.

So, I started looking for libraries that would give me a Should()-like syntax with NUnit but I didn't have much luck. I found NBehave, but it offers more than I need and it required .NET 3.5 (and I want to be able to support .NET 2.0). I also found some projects on github, but 1 had no code and another didn't implement many Should() methods

I wanted a way to integrate nicely with NUnit's Assert.That constraints so that, out of the box, I should be able to write 5.Should(Be.EqualTo(5)) without implementing the EqualTo method myself, but just use NUnit's!

So NUnit.Should was born.

The Code

The code is so tiny that I pasted it right here in the README. There are also some Should*() [helper methods][] available, but this is the main NUnit.Should code.

using System;
using System.Collections;
using NUnit.Framework.Constraints;

namespace NUnit.Framework {

    public class Be      : Is       { public Be(){} }
    public class Have    : Has      { public Have(){} }
    public class Contain : Contains { public Contain(){} }

    public static partial class ShouldExtensions {
        public static void Should(this object o, IResolveConstraint constraint) {
            Assert.That(o, constraint);
        public static void ShouldNot(this object o, Constraint constraint) {
            Assert.That(o, new NotOperator().ApplyPrefix(constraint));

That's it! That let's you say 5.Should(Be.EqualTo(5)) instead of Assert.That(5, Is.EqualTo(5)). Couldn't be simpler!


NUnit.Should is released under the MIT license.

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