// Arrange Act Assert

Jag Reehal on Agile Development, ASP.NET MVC and all manner of good stuff

Ever Thought About Changing How You Name Unit Tests?

Posted on | January 11, 2010 | No Comments

In the last couple of months I’ve seen a new convention of how developers are naming their unit test classes.

Traditionally the naming convention most developers use is to append the word ‘Tests’ to the class name as shown below.

public class UserValidation
{
}

[TestFixture]
public class UserValidationTests
{
}

There is absolutely nothing wrong with it, but this can lead to problems because a test class can become unwieldy and difficult to maintain either because it’s too long, testing a lot of different concerns or both.

In some cases it would make more sense to take different approach and adopt an alternative naming convention. Sticking with the example above instead of having tests for validating a user in one class, a new class could be created for each concern. So instead of 

using System;
using NUnit.Framework;
using NBehave.Spec.NUnit;

namespace MyApplication.Validation
{
    [TestFixture]
    public class UserValidationTests
    {
        [Test]
        public void Should_Return_False_When_Username_Length_Is_To_Short()
        {
            // Arrange
            UserValidation userValidation = new UserValidation();

            // Act
            bool result = userValidation.IsUsernameValid(string.Empty);

            // Assert
            result.ShouldEqual(false);
        }

        [Test]
        public void Should_Return_False_When_Username_Length_Is_To_Long() { }

        [Test]
        public void Should_Return_False_When_Username_Contains_Invalid_Characters() { }

        [Test]
        public void Should_Return_True_When_Username_Is_Valid() { }

        [Test]
        public void Should_Return_False_When_Password_Length_Is_To_Short() { }

        [Test]
        public void Should_Return_False_When_Password_Length_Is_To_Long() { }

        [Test]
        public void Should_Return_False_When_Password_Is_Just_Numbers()
        {
            // Arrange
            UserValidation userValidation = new UserValidation();

            // Act
            bool result = userValidation.IsPasswordValid("123456");

            // Assert
            result.ShouldEqual(false);
        }

        [Test]
        public void Should_Return_False_When_Password_Is_Just_Alphabetical_Characters() { }

        [Test]
        public void Should_Return_False_When_Password_Contains_Invalid_Characters() { }

        [Test]
        public void Should_Return_True_When_Password_Is_Valid() { }
    }
}

we create two test classes

using System;
using NUnit.Framework;
using NBehave.Spec.NUnit;

namespace MyApplication.Validation
{
    [TestFixture]
    public class When_Validating_A_Users_Username
    {
        [Test]
        public void Should_Return_False_When_Username_Length_Is_To_Short()
        {
            // Arrange
            UserValidation userValidation = new UserValidation();

            // Act
            bool result = userValidation.IsUsernameValid(string.Empty);

            // Assert
            result.ShouldEqual(false);
        }

        [Test]
        public void Should_Return_False_When_Username_Length_Is_To_Long() { }

        [Test]
        public void Should_Return_False_When_Username_Contains_Invalid_Characters() { }

        [Test]
        public void Should_Return_True_When_Username_Is_Valid() { }
    }

    [TestFixture]
    public class When_Validating_A_Users_Password
    {
        [Test]
        public void Should_Return_False_When_Password_Length_Is_To_Short() { }

        [Test]
        public void Should_Return_False_When_Password_Length_Is_To_Long() { }

        [Test]
        public void Should_Return_False_When_Password_Is_Just_Numbers()
        {
            // Arrange
            UserValidation userValidation = new UserValidation();

            // Act
            bool result = userValidation.IsPasswordValid("123456");

            // Assert
            result.ShouldEqual(false);
        }

        [Test]
        public void Should_Return_False_When_Password_Is_Just_Alphabetical_Characters() { }

        [Test]
        public void Should_Return_False_When_Password_Contains_Invalid_Characters() { }

        [Test]
        public void Should_Return_True_When_Password_Is_Valid() { }
    }
}

I think this behavior driven development type naming convention will help focus on the problem you are solving and nothing more. This is very useful when doing test driven development.

When I first saw tests written like this my first thought was how am I going to find the all the tests for User Validation because they are no longer in a single class? If this is a problem for you think about using namespaces, folders or test attributes to organise your tests. Don’t forget if you use tools like ReSharper help you find where a class is being used very easily.

Remember this is about renaming your tests classes and not your methods. So even if you follow the MethodName_StateUnderTest_ExpectedBehavior pattern for test methods this could still work.

Category: Unit tests

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