A .NET Unit Test without a parameterless constructor, to facilitate dependency injection

Question

I\'m trying to have the unit tests not rely on calling container.Resolve() for their dependencies.

I\'m currently using AutoFac 2.2.4,

Answer 1

I just allow my tests to have a dependency on Autofac, although I encapsulate it. All of my TestFixtures inherit from Fixture, which is defined as such:

public class Fixture
{
    private static readonly IContainer MainContainer = Ioc.Build();
    private readonly TestLifetime _testLifetime = new TestLifetime(MainContainer);

    [SetUp]
    public void SetUp()
    {
        _testLifetime.SetUp();
    }

    [TearDown]
    public void TearDown()
    {
        _testLifetime.TearDown();
    }

    protected TService Resolve()
    {
        return _testLifetime.Resolve();
    }

    protected void Override(Action configurationAction)
    {
        _testLifetime.Override(configurationAction);
    }
}

public class TestLifetime
{
    private readonly IContainer _mainContainer;

    private bool _canOverride;
    private ILifetimeScope _testScope;

    public TestLifetime(IContainer mainContainer)
    {
        _mainContainer = mainContainer;
    }

    public void SetUp()
    {
        _testScope = _mainContainer.BeginLifetimeScope();
        _canOverride = true;
    }

    public void TearDown()
    {
        _testScope.Dispose();
        _testScope = null;
    }

    public TService Resolve()
    {
        _canOverride = false;
        return _testScope.Resolve();
    }

    public void Override(Action configurationAction)
    {
        _testScope.Dispose();

        if (!_canOverride)
            throw new InvalidOperationException("Override can only be called once per test and must be before any calls to Resolve.");

        _canOverride = false;
        _testScope = _mainContainer.BeginLifetimeScope(configurationAction);
    }
}