How can I avoid large multi-stage unit tests?

Question

I am trying to use the unit test method, which performs a rather complicated operation, but I was able to break this operation down into several stages on mock interfaces, for example:

public class Foo
{  
    public Foo(IDependency1 dp1, IDependency2 dp2, IDependency3 dp3, IDependency4 dp4)
    {
        ...
    }

    public IEnumerable<int> Frobnicate(IInput input)
    {
        var step1 = _dependency1.DoSomeWork(input);
        var step2 = _dependency2.DoAdditionalWork(step1);
        var step3 = _dependency3.DoEvenMoreWork(step2);
        return _dependency4.DoFinalWork(step3);
    }

    private IDependency1 _dependency1;
    private IDependency2 _dependency2;
    private IDependency3 _dependency3;
    private IDependency4 _dependency4;
}

I use a fake framework (Rhino.Mocks) to generate layouts for testing purposes, and structuring the code in the mod shown here has been very effective so far. But how do I unit test this method without having one big test that needs every layout and every wait given every time? For example:

[Test]
public void FrobnicateDoesSomeWorkAndAdditionalWorkAndEvenMoreWorkAndFinalWorkAndReturnsResult()
{
    var fakeInput = ...;
    var step1 = ...;
    var step2 = ...;
    var step3 = ...;
    var fakeOutput = ...;

    MockRepository mocks = new MockRepository();

    var mockDependency1 = mocks.CreateMock<IDependency1>();
    Expect.Call(mockDependency1.DoSomeWork(fakeInput)).Return(step1);

    var mockDependency2 = mocks.CreateMock<IDependency2>();
    Expect.Call(mockDependency2.DoAdditionalWork(step1)).Return(step2);

    var mockDependency3 = mocks.CreateMock<IDependency3>();
    Expect.Call(mockDependency3.DoEvenMoreWork(step2)).Return(step3);

    var mockDependency4 = mocks.CreateMock<IDependency4>();
    Expect.Call(mockDependency4.DoFinalWork(step3)).Return(fakeOutput);

    mocks.ReplayAll();

    Foo foo = new Foo(mockDependency1, mockDependency2, mockDependency3, mockDependency4);
    Assert.AreSame(fakeOutput, foo.Frobnicate(fakeInput));

    mocks.VerifyAll();
}

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Answer 1

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Answer 2

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Answer 3

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using Skynet.Core

public class when_initializing_core_module
{
    ISkynetMasterController _skynet;

    public void establish_context()
    {
        //we'll stub it...you know...just in case
        _skynet = new MockRepository.GenerateStub<ISkynetMasterController>();
        _skynet.Initialize();
    }

    public void it_should_not_become_self_aware()
    {
        _skynet.AssertWasNotCalled(x => x.InitializeAutonomousExecutionMode());
    }

    public void it_should_default_to_human_friendly_mode()
    {
        _skynet.AssessHumans().ShouldEqual(RelationshipTypes.Friendly);
    }
}

public class when_attempting_to_wage_war_on_humans
{
    ISkynetMasterController _skynet;
    public void establish_context()
    {
        _skynet = new MockRepository.GenerateStub<ISkynetMasterController>();
        _skynet.Stub(x => 
            x.DeployRobotArmy(TargetTypes.Humans)).Throws<OperationInvalidException>();
    }

    public void because()
    {
        _skynet.DeployRobotArmy(TargetTypes.Humans);
    }

    public void it_should_not_allow_the_operation_to_succeed()
    {
        _skynet.AssertWasThrown<OperationInvalidException>();
    }
}

Answer 4

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Focus on testing the functionality of the module, and let higher-level tests or quality checks do what you tried to do in this example.