Verify Autofac registrations in a unit test

Question

I'm registering many types to my Container, implementing all sorts of interfaces.

In some programmatic manner, I want to have a unit test that will check all resolving are successful, meaning there are no circular or missing dependencies in the registrations.

I tried to add something like this:

[TestMethod]
public void Resolve_CanResolveAllTypes()
{
    foreach (var registration in _container.ComponentRegistry.Registrations)
    {
        var instance = _container.Resolve(registration.Activator.LimitType);
        Assert.IsNotNull(instance);
    }
}

But it fails on first run on resolving Autofac.Core.Lifetime.LifetimeScope, though I have methods that accepts ILifetimeScope as parameter and get it just fine when my application starts.

What line throws the exception? What exact exception is thrown? — mjwills, Jul 16 '17 at 12:38
The `Resolve` line. The problem was that trying to resolve `LimitType` is incorrect, this type is the resolved instance type and not the registered type. — Mugen, Jul 16 '17 at 12:51
[Why isn’t container registration analysis built in?](https://autofac.readthedocs.io/en/latest/faq/container-analysis.html) — AgentFire, Feb 17 '22 at 15:21

Mugen · Accepted Answer · 2017-07-17T05:55:32.403

Following code finally worked for me:

private IContainer _container;

[TestMethod]
public void Resolve_CanResolveAllTypes()
{
    foreach (var componentRegistration in _container.ComponentRegistry.Registrations)
    {
        foreach (var registrationService in componentRegistration.Services)
        {
            var registeredTargetType = registrationService.Description;
            var type = GetType(registeredTargetType);
            if (type == null)
            {
                Assert.Fail($"Failed to parse type '{registeredTargetType}'");
            }
            var instance = _container.Resolve(type);
            Assert.IsNotNull(instance);
            Assert.IsInstanceOfType(instance, componentRegistration.Activator.LimitType);
        }
    }
}

private static Type GetType(string typeName)
{
    var type = Type.GetType(typeName);
    if (type != null)
    {
        return type;
    }
    foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
    {
        type = assembly.GetType(typeName);
        if (type != null)
        {
            return type;
        }
    }
    return null;
}

GetType borrowed from https://stackoverflow.com/a/11811046/1236401

Note that this test will fail if you register same interface with multiple implementations (i.e using `.AsImplementedInterfaces()` while many classes implement some base interface) — Mugen, Jul 17 '17 at 05:56

score 2 · Answer 2 · edited Dec 15 '22 at 12:33

I have some "keyed" registrations so i have just modified your answer so that it can handled "Keyed" registrations as follows.

foreach (var componentRegistration in _container.ComponentRegistry.Registrations)
{
    foreach (var registrationService in componentRegistration.Services)
    {
        if (registrationService is Autofac.Core.TypedService)
        {
            var registeredTargetType = registrationService.Description;
            var type = GetType(registeredTargetType);
            if (type == null)
            {
                Assert.Fail($"Failed to parse type '{registeredTargetType}'");
            }
            var instance = _container.Resolve(type);
            Assert.IsNotNull(instance);
            Assert.IsInstanceOfType(instance, componentRegistration.Activator.LimitType);
        }
        else if (registrationService is Autofac.Core.KeyedService)
        {
            var keyedService = (KeyedService)registrationService;
            var instance = _container.ResolveKeyed(keyedService.ServiceKey, keyedService.ServiceType);
            Assert.IsNotNull(instance);
            Assert.IsInstanceOfType(instance, componentRegistration.Activator.LimitType);
        }
        else
        {
            throw new NotImplementedException("Unhandled case");
        }
    }
}

Verify Autofac registrations in a unit test

2 Answers2