.NET core write better unit tests with Xunit + Autofixture + Moq

Question

In .NET Core for unit testing, I'm using Xunit, Moq, and Autofixture. But even with them, I see that my unit tests become complicated and take time.

Maybe someone could tell me if there are any ways to make this test smaller?

[Fact]
public async Task Verify_NotAuthorised_NoServiceSendInvoked()
{
    // Arrange
    var fixture = new Fixture()
        .Customize(new AutoMoqCustomization());

    var sut = fixture.Create<VerificationService>();

    var mockApiBuilder = fixture.Freeze<Mock<IApiEntityBuilder>>();
    //init mocked mockSendServiceOne, so later I could check if it was invoked or not
    var mockSendServiceOne = fixture.Freeze<Mock<ISendServiceOne>>();

    mockApiBuilder.Setup(x => x.Verification(It.IsAny<string>(), It.IsAny<string>()))
        .Returns(fixture.Create<VerificationEntity>());

    var call = fixture.Freeze<Mock<ISendServiceTwo>>();
    call.Setup(x => x.IsSuccessful()).Returns(false);

    // Act
    await sut.Verify(fixture.Create<string>(), fixture.Create<string>());

    // Assert
    mockSendServiceOne.Verify(x => x.Call(It.IsAny<SendServiceOneEntity>()), Times.Never);
}

The testing method itself

public async Task<CreatedEntity> Verify(string dataOne, string dataTwo)
{
   await _someCaller.Call(_apiEntityBuilder.Verification(dataOne, dataTwo));
   _someCaller.CreatePayment();

   if (!_someCaller.IsSuccessful()) return _someCaller.CreatedEntity;

   await mockSendServiceOne.Call(_apiEntityBuilder.Call(_someCaller.CreatedEntity.SpecificData));

   return _someCaller.CreatedEntity;
}

Here I am testing if isSuccessful() returns fasle then no mockSendServiceOne.Call should be invoked.

Could someone give me some feedback on how to write a better unit tests. Because only for this small check of code I had to write a lot of code to test it.

How much code for unit test would be "good" amount of code, so you wouldn't worried about it? — Fabio
– Fabio, Commented Oct 2, 2019 at 8:16
Maybe I say in other words, this test to write took me about 25-30min and is it okay? So I would like to get some feedback from others, is it a good test or should investigate in my code design or unit test structure. For instance, I am trying to keep my service classes containing max 2-3 dependencies so my test would not be heavy. — Andrius
– Andrius, Commented Oct 2, 2019 at 8:23
*Testing the same method but different outputs/states, to be more clearly — Andrius
– Andrius, Commented Oct 2, 2019 at 12:23

Magnus · Accepted Answer · 2019-10-09 05:51:42Z

5

You can use AutoData Theories. (Links to a great post by Mark Seeman about this exact situation).

In short AutoFixture has a built in attribute called AutoData which you can inherit from and then customize the fixture with the AutoMoqCustomization.

You decorate your testmethod ([Theory]) with this attribute, and now autofixture automagically will generate any parameter you specify for your testmethod.

When you would use the Freeze() method to generate an item, you put the [Frozen]attribute in front of the parameter.

Here is an example of how to do it:

public class TheTests
{
    [Theory]
    [AutoDomainData]
    public void Verify_WhatWeWannaTest_CallsTheMethodOnTheDependency([Frozen] Mock<ITheDependency> dependency, WhatWeWannaTest sut)
    {
        // Act
        sut.CallTheDependency();

        // Assert
        dependency.Verify(x => x.TheMethod());
    }
}

// Create a AutoData attribute customized with Moq
public class AutoDomainDataAttribute : AutoDataAttribute
{
    public static IFixture FixtureFactory()
    {
        var f = new Fixture();
        // I like members of interfaces to be configured, so i set it her
        f.Customize(new AutoMoqCustomization { ConfigureMembers = true });
        return f;
    }

    public AutoDomainDataAttribute() : base(FixtureFactory) { }
}

// Simple class we can test
public class WhatWeWannaTest
{
    private readonly ITheDependency _theDependency;

    public WhatWeWannaTest(ITheDependency theDependency) { _theDependency = theDependency; }

    public void CallTheDependency()
    {
        _theDependency.TheMethod();
    }
}

// Simple dependency for WhatWeWannaTest
public interface ITheDependency
{
    int TheMethod();
}

answered Oct 9, 2019 at 5:51

Magnus

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4 Comments

Andrius Over a year ago

What if I want to declare a fake object with some specific fields using AutoDataAttribute? Because in the method scope I can't change a fixture instance. Doesn't it limit all the benefit giving from autofixture?

Andrius Over a year ago

Of course, I can change object's property by myself without any fixture after, but still, I see that not all functionality will be available for me in a simple way using attribute

Magnus Over a year ago

If you want your mocks to have a certain default behaviour across tests, I would customize the types in the FixtureFactory. When I need to do a little more advanced stuff with the fixture (which is seldom) I ask for an instance of the fixture e.g.: TestMethod(IFixture fixture). Then I get a customized fixture, from the FixtureFactory. @Andrius

Andrius Over a year ago

I didn't know that it's possible to get IFixture instance from the method's parameters. Great!

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