Fixie is a .NET convention-based test framework similar to NUnit and xUnit, but with an emphasis on low-ceremony defaults and flexible customization. Fixie's development is documented at http://plioi.github.io/fixie.

First, install NuGet. Then, install the Fixie NuGet package from the package manager console:

PM> Install-Package Fixie

1. Create a Class Library project to house your test classes.

2. Add a reference to Fixie.dll.

3. Add test classes and test cases to your testing project.

4. Use the console runner (should be at your-solution-dir/packages/Fixie.x.x.x/lib/netXX/) from a command line to execute your tests:

   Fixie.Console.exe path/to/your/test/project.dll

5. Use the TestDriven.NET runner from within Visual Studio, using the same keyboard shortcuts you would use for NUnit tests.

When using the default convention, a test class is any concrete class in your test assembly whose name ends with "Tests". Within such a test class, a test case is any public instance void method. Additionally, test cases include public instance async methods returning Task or Task<T>.

One instance of your test class is constructed for each test case. To perform setup steps before each test case executes, use the test class's default constructor. To perform cleanup steps after each test cases executes, implement IDisposable and place cleanup code within the Dispose() method.

No [Attributes], no "using Fixie;" statement, no muss, no fuss.

using Should;

public class CalculatorTests
{
    readonly Calculator calculator;

    public CalculatorTests()
    {
        calculator = new Calculator();
    }

    public void ShouldAdd()
    {
        calculator.Add(2, 3).ShouldEqual(5);
    }

    public void ShouldSubtract()
    {
        calculator.Subtract(5, 3).ShouldEqual(2);
    }

    public async Task SupportsAsyncTestCases()
    {
        int result = await AddAsync(2, 3);

        result.ShouldEqual(5);
    }

    private Task<int> AddAsync(int x, int y)
    {
        return Task.Run(() => calculator.Add(x, y));
    }
}

Although useful for simple scenarios, the default convention may not meet your needs. Fortunately, you can replace it with your own.

If you don't want to go with the behaviors defined in the default convention, simply place a subclass of Convention beside your tests. A custom subclass of Convention will reach out into the containing test assembly, looking for tests to execute. Each convention can customize test discovery and test execution. For test discovery, you describe what your test classes and test methods look like. For test execution, you can take control over how frequently your test classes are constructed and how they are constructed. Additionally, you can wrap custom behavior around each test method, around each test class instance, and around each test class.

For instance, let's say we want all of our integration tests to be automatically wrapped in a database transaction. Beside our tests, we place a custom convention class:

using Fixie;
using Fixie.Conventions;

namespace IntegrationTests
{
    public class IntegrationTestConvention : Convention
    {
        public IntegrationTestConvention()
        {
            Classes
                .NameEndsWith("Tests");

            Methods
                .Where(method => method.IsVoid());

            InstanceExecution
                .Wrap((fixture, innerBehavior) =>
                {
                    using (new TransactionScope())
                        innerBehavior();
                });
        }
    }
}

Several sample conventions are available under the Fixie.Samples project:

• Imitate NUnit
• Imitate xUnit
• Simplified NUnit for cleaner test inheritance
• Construct integration test classes with your IoC container
• Support arbitrary command line flags such as NUnit-style categories

With the default convention, Fixie is unable to run parameterized test methods, because it doesn't know where those input parameters should come from. In a custom convention, though, you can define the meaning of parameterized test methods.

In a custom convention, use the Parameters(...) method to define the origin of test method parameters. Parameters(...) accepts a delegate of type Func<MethodInfo, IEnumerable<object[]>>. In other words, for any given method, your delegate must produce a series of object arrays. Each object array corresponds with a single call to the test method.

You may want parameters to come from attributes, your IoC container, AutoFixture, metadata from the filesystem... anything that yields object arrays.

Let's say you want test method parameters to come from [Input] attributes. Define InputAttribute:

[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
public class InputAttribute : Attribute
{
    public InputAttribute(params object[] parameters)
    {
        Parameters = parameters;
    }
 
    public object[] Parameters { get; private set; }
}

Next, place InputAttributes on parameterized tests.

public class CalculatorTests
{
    readonly Calculator calculator;
 
    public CalculatorTests()
    {
        calculator = new Calculator();
    }
 
    [Input(2, 3, 5)]
    [Input(3, 5, 8)]
    public void ShouldAdd(int a, int b, int expectedSum)
    {
        calculator.Add(a, b).ShouldEqual(expectedSum);
    }
 
    [Input(5, 3, 2)]
    [Input(8, 5, 3)]
    [Input(10, 5, 5)]
    public void ShouldSubtract(int a, int b, int expectedDifference)
    {
        calculator.Subtract(a, b).ShouldEqual(expectedDifference);
    }
}

Lastly, define a custom convention which passes a Func<MethodInfo, IEnumerable<object[]>> to Parameters(...):

public class CustomConvention : Convention
{
    public CustomConvention()
    {
        Classes
            .NameEndsWith("Tests");

        Methods
            .Where(method => method.IsVoid());

        Parameters(FromInputAttributes);
    }

    static IEnumerable<object[]> FromInputAttributes(MethodInfo method)
    {
        return method.GetCustomAttributes<InputAttribute>(true).Select(input => input.Parameters);
    }
}

When the system under test uses generics, you may want your parameterized test method to be generic as well. If a parameterized method happens to be a generic method, Fixie compares the runtime type of each incoming parameter value against the generic method declaration in order to pick the best concrete type for each generic type parameter. This step is necessary because reflection does not allow you to simply pass an object[] of parameter values when invoking a generic method thorugh its MethodInfo. Fixie must first convert the generic method definition's MethodInfo into a more specific MethodInfo with the type arguments resolved. For instance, consider what happens when we have a generic test method using the [Input] attribute as defined above:

[Input(true)]
[Input(1)]
[Input("A")]
public void GenericTestMethod<T>(T input)
{
    Console.WriteLine(typeof(T).Name);
}

The output of running this test method is:

Boolean
Int32
String

Instead of receiving the input as an object each time, the correct concrete type is substituted for the T. If there is any ambiguity over what concrete type should be selected, though, object will be assumed.

Don't skip tests.

No, really, how do I skip tests?

The default convention does not support skipped tests. In a custom convention, use the Skip(...) method to define what makes a test skipped. Skip(...) accepts a delegate of type Func<Case, bool>. In other words, for any given test case, your delegate must return true when the test case should be skipped.

You may want to skip based on an attribute, an attribute with an expiration date, a naming convention, or some other rule. Here we define a [Skip] attribute and a custom convention which looks for it on test methods:

[AttributeUsage(AttributeTargets.Method, Inherited = false, AllowMultiple = false)]
public class SkipAttribute : Attribute { }

public class CustomConvention : Convention
{
    public CustomConvention()
    {
        Classes
            .NameEndsWith("Tests");
     
        Methods
            .Where(method => method.IsVoid());
     
        CaseExecution
            .Skip(@case => @case.Method.HasOrInherits<SkipAttribute>());
    }
}

Now, any test method marked with [Skip] will be skipped by the test runner.

Most test frameworks such as NUnit or xUnit include their own assertion libraries so that you can make statements like this:

Assert.AreEqual(expected, actual);

Assertion libraries are orthogonal to test frameworks. Your choice of assertion library should be independent of your choice of test framework. Therefore, Fixie will never include an assertion library.

Here are some useful third-party assertion libraries:

• Should
• Shouldly
• Fluent Assertions