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More fluent assertions using extension methods

I'm a great believer in making your unit tests as easy to read and understand as possible. I was thinking about how I could improve my tests the other day and thought about using extension methods to create a more fluent way of creating complex assertions.

This has allowed me to create a complex assertion like:

  1. testObject.ShouldBeTheSameObjectAs(targetObject).And.ShouldBeEqualTo(testObject).And.ShouldSatisfy(x => x is Object);

Which I hope you'll agree reads a lot easier than those three assumptions on separate lines. Also, note that I have added the ability to use a predicate for when there isn't a method which quite matches your needs.

Here's the code for the extension methods:

  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. using MbUnit.Framework;
  6.  
  7. namespace UnitTestingExtensions
  8. {
  9.     public static class FluentTestingExtensions
  10.     {
  11.         public static FluentAnd<T> ShouldSatisfy<T>(this T testTarget, Predicate<T> predicate)
  12.         {
  13.             Assert.IsTrue(predicate.Invoke(testTarget));
  14.             return new FluentAnd<T>(testTarget);
  15.         }
  16.  
  17.         public static FluentAnd<T> ShouldBeEqualTo<T>(this T testTarget, T comparisonObject)
  18.         {
  19.             Assert.AreEqual(testTarget, comparisonObject);
  20.             return new FluentAnd<T>(testTarget);
  21.         }
  22.  
  23.         public static FluentAnd<T> ShouldBeTheSameObjectAs<T>(this T testTarget, Object comparisonObject)
  24.         {
  25.             Assert.AreEqual(testTarget, comparisonObject);
  26.             return new FluentAnd<T>(testTarget);
  27.         }
  28.  
  29.         public class FluentAnd<T>
  30.         {
  31.             public T And { get; private set; }
  32.  
  33.             public FluentAnd(T target)
  34.             {
  35.                 this.And = target;
  36.             }
  37.         }
  38.     }
  39.  
  40. }

And here are the tests for the extension methods:

  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. using MbUnit.Framework;
  6.  
  7. namespace UnitTestingExtensions.FluentTestingExtensionsTests
  8. {
  9.     [TestFixture]
  10.     public class ShouldSatisfyTests
  11.     {
  12.         [Test, ExpectedException(typeof(MbUnit.Core.Exceptions.AssertionException))]
  13.         public void PredicateEvaluatesAsFalseAndTestFails()
  14.         {
  15.             int testNumber = 4;
  16.  
  17.             testNumber.ShouldSatisfy(x => x > 10);
  18.         }
  19.  
  20.         [Test]
  21.         public void PredicateEvaluatesAsTrueAndTestPasses()
  22.         {
  23.             int testNumber = 4;
  24.  
  25.             testNumber.ShouldSatisfy(x => x == 4);
  26.         }
  27.     }
  28.  
  29.     [TestFixture]
  30.     public class ShouldBeEqualToTests
  31.     {
  32.         [Test, ExpectedException(typeof(MbUnit.Core.Exceptions.AssertionException))]
  33.         public void EqualsCheckFailsAndTestFails()
  34.         {
  35.             int testNumber = 4;
  36.  
  37.             testNumber.ShouldBeEqualTo(7);
  38.         }
  39.  
  40.         [Test]
  41.         public void EqualsCheckPassesAndTestPasses()
  42.         {
  43.             int testNumber = 4;
  44.  
  45.             testNumber.ShouldBeEqualTo(4);
  46.         }
  47.     }
  48.  
  49.     [TestFixture]
  50.     public class ShouldBeTheSameObjectAsTests
  51.     {
  52.         [Test, ExpectedException(typeof(MbUnit.Core.Exceptions.AssertionException))]
  53.         public void DifferentObjectsSoTestFails()
  54.         {
  55.             Object testObject = new Object();
  56.  
  57.             testObject.ShouldBeTheSameObjectAs(new Object());
  58.         }
  59.  
  60.         [Test]
  61.         public void TestPassesWhenTheObjectsAreTheSame()
  62.         {
  63.             Object testObject = new Object();
  64.             Object checkObject = testObject;
  65.  
  66.             testObject.ShouldBeTheSameObjectAs(checkObject);
  67.         }
  68.     }
  69.  
  70.     [TestFixture]
  71.     public class AndTests
  72.     {
  73.         [Test, ExpectedException(typeof(MbUnit.Core.Exceptions.AssertionException))]
  74.         public void TestFailsIfFirstCaseFails()
  75.         {
  76.             int testNumber = 4;
  77.  
  78.             testNumber.ShouldBeEqualTo(3).And.ShouldSatisfy(x => x > 1);
  79.         }
  80.  
  81.         [Test, ExpectedException(typeof(MbUnit.Core.Exceptions.AssertionException))]
  82.         public void TestFailsIfSecondCaseFails()
  83.         {
  84.             int testNumber = 4;
  85.  
  86.             testNumber.ShouldBeEqualTo(4).And.ShouldSatisfy(x => x > 10);
  87.         }
  88.  
  89.         [Test]
  90.         public void TestPassesIfBothCasesPass()
  91.         {
  92.             int testNumber = 4;
  93.  
  94.             testNumber.ShouldSatisfy(x => x > 1).And.ShouldBeEqualTo(4);
  95.         }
  96.  
  97.         [Test]
  98.         public void TestPassesWhenThreeCasesAreUsed()
  99.         {
  100.             Object testObject = new Object();
  101.             Object targetObject = testObject;
  102.  
  103.             testObject.ShouldBeTheSameObjectAs(targetObject).And.ShouldBeEqualTo(testObject).And.ShouldSatisfy(x => x is Object);
  104.         }
  105.     }
  106. }

I'd love to hear some feedback on what you think of this style.

My version of a SmartBag

After seeing Jeffrey Palermo's SmartBag (part 1 and part 2) I was inspired to create my own version which was more specific to my needs. For one I'm a lover of the IEnumerable<T> interface, especially when combined with the power of LINQ for Objects.

Anyway, enough of my waffle, here's the code for the class.

  1. using System;
  2. using System.Collections.Generic;
  3. using System.Collections;
  4. using System.Text;
  5.  
  6. namespace SmartBag
  7. {
  8.     public class SmartBag
  9.     {
  10.         private Hashtable _hashtable;
  11.  
  12.         public SmartBag()
  13.         {
  14.             this._hashtable = new Hashtable();
  15.         }
  16.  
  17.         public void Add<T>(T item)
  18.         {
  19.             List<T> list;
  20.  
  21.  
  22.             if (!this._hashtable.ContainsKey(typeof(T)))
  23.                 this._hashtable.Add(typeof(T), new List<T>());
  24.  
  25.             list = this._hashtable[typeof(T)] as List<T>;
  26.             list.Add(item);
  27.         }
  28.  
  29.         public IEnumerable<T> Get<T>()
  30.         {
  31.             if (!this._hashtable.ContainsKey(typeof(T)))
  32.                 throw new IndexOutOfRangeException(string.Format("There are no entries for {0}", typeof(T).Name));
  33.  
  34.             foreach (T item in this._hashtable[typeof(T)] as List<T>)
  35.                 yield return item;
  36.         }
  37.     }
  38. }

There are basically two methods to it, Add and Get. Add adds items of the specified type to a list of that type. Get retrieves the list of the specified type.

Below are my test cases which should give you some ideas of how you can use it.

  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. using MbUnit.Framework;
  6.  
  7. namespace SmartBag
  8. {
  9.     [TestFixture]
  10.     class SmartBagTest
  11.     {
  12.         [Test]
  13.         public void AClassAddedAgainstAnInterfaceCanBeRetrievedTogether()
  14.         {
  15.             SmartBag bag = new SmartBag();
  16.  
  17.  
  18.             bag.Add<IContract>(new Parent());
  19.             bag.Add<IContract>(new Child());
  20.  
  21.             Assert.AreEqual(2, bag.Get<IContract>().Count());
  22.         }
  23.  
  24.         [Test]
  25.         public void AChildWillBeAddedToItsParentsEnumerationIfYouDefineIt()
  26.         {
  27.             SmartBag bag = new SmartBag();
  28.  
  29.  
  30.             bag.Add(new Parent());
  31.             bag.Add<Parent>(new Child());
  32.  
  33.             Assert.AreEqual(2, bag.Get<Parent>().Count());
  34.         }
  35.  
  36.         [Test, ExpectedException(typeof(IndexOutOfRangeException))]
  37.         public void AnExpectionWillBeRaiseWhenAttemptingToRetrieveATypeThatDoesNotExist()
  38.         {
  39.             SmartBag bag = new SmartBag();
  40.  
  41.  
  42.             foreach (Object item in bag.Get<Object>()) { } // must enumerate for it to be evaluated
  43.         }
  44.  
  45.         [Test]
  46.         public void ShouldBeAbleToAddChildAsADifferentType()
  47.         {
  48.             SmartBag bag = new SmartBag();
  49.  
  50.  
  51.             bag.Add(new Parent());
  52.             bag.Add(new Child());
  53.  
  54.             Assert.AreEqual(1, bag.Get<Parent>().Count());
  55.             Assert.AreEqual(1, bag.Get<Child>().Count());
  56.         }
  57.  
  58.         private class Parent : IContract
  59.         {
  60.         }
  61.  
  62.         private class Child : Parent
  63.         {
  64.         }
  65.  
  66.         private interface IContract
  67.         {
  68.         }
  69.     }
  70. }

To begin with this is a basic idea. I hope to utilise it in an upcoming project and it will probably look a bit different after I've used it in anger. Something I can see I might need is to extract an interface to make testing easier but I've left that out for now as YAGNI may apply.

Any feedback would be greatly appreciated.