Wednesday, November 5, 2014

Using different containers with Chill

When Chill 1.0 wanted to know which container (for example the Chill.AutofacNSubstitute container) it needed to use, it would scan your loaded assemblies for types that implemented the IChillContainer. While this worked, it also posed several issues.

For one, you couldn’t use different types of chill containers. For example, if you wanted to have tests with several containers that do automocking, some without automocking, some with very specific registrations set up), you couldn’t do that.

The other issue had to do with portable class libraries. I wanted to make Chill a portable class library. For example if you wanted to test Xamarin IOS classes (without turning them into PCL’s), then you can only reference PCL’s or Xamarin IOS dll’s from your test project.

But, to turn Chill into a PCL, I had to change the way it did assembly scanning. PCL’s have quite a lot of restrictions with regards to assembly scanning.

However, I think the end result is quite elegant.

Basically, if you install a specific container, Chill will add an assembly level attribute, in a file called DefaultChillContainer:

// This attribute defines which container will be used by default for this assembly

[assembly: ChillContainer(typeof(AutofacNSubstituteChillContainer))]


This tells Chill to use this container (in this case an AutoMocking container using NSubstitute) as the default container. Now, if you want to use a different container in some situations, you can override this on a per test basis:


public class When_configuring_container_with_module_and_objectmother : GivenWhenThen

Under the covers, Chill will wrap the container you specify in a AutoMotherDecorator (more on AutoMothers in a later blog post). If you don’t want this, then you can specify a custom ChillContainerInitializer:



The DefaultChillContainerInitializer is the class that wraps the ChillContainer the AutoMotherDecorator, so you can implement your own class if you don’t like this behavior. Now I don’t expect that this happens often, but it’s nice to have the option.

As always, keep it cool, keep it Chill!

Integration testing with Chill


Unit testing means testing software components in isolation. This can be a powerful technique to validate some complex pieces of logic.

However, if you follow the Single Responsibility Principle, you’ll find that many of your components hardly contain enough logic to warrant unit testing. For example, a webapi controller might just take a message object, validate it using a validator component, map it to an internal data format, and then hand it off to yet another component for validation. All it does is chain some components together. If you dogmatically try to unit test each of these components in isolation, you’ll end up with a system that becomes difficult to architecturally.

In those cases, integration tests make much more sense. You want to make sure that the entire collection of components work well together, not that each individual piece does what it needs to do.

Note, unit tests do make a lot of sense for some (sufficiently complex) components. As always, it’s important to know what technique to apply when.

Integration testing does have it’s own set of challenges. Ideally, you’d like to start with a pristine environment, prepare a certain ‘start situation’, then execute a test and validate the result. In the next couple of weeks, I’ll put out a sample application that demonstrates some of these capabilities.

But for now, I can demonstrate how you can setup a container in exactly the same way that you’d do in your application.

Suppose you have several registrations you’d like to make in your container. Here, I’m doing that in Autofac in a module:

   2: public class CustomAutofacModule : Module
   3: {
   4:     protected override void Load(ContainerBuilder builder)
   5:     {
   6:         builder.RegisterType<TestService>().As<ITestService>();
   7:         builder.RegisterType<TestSingleton>().SingleInstance();
   8:         base.Load(builder);
   9:     }
  10: }

Ok, great.. now how would you set up a chill container that uses this? The easiest way is to create a custom container, that derives from  AutofacChilContainer. 

   1: /// <summary>
   2: /// You can define 'non mocking' with all the type registrations that you would otherwise in your application. 
   3: /// This can either be done in the App. This class also creates a single 'parent' container and then child containers
   4: /// per test. 
   5: /// </summary>
   6: internal class AutofacContainerWithCustomModule : AutofacChillContainer
   7: {
   8:     private static ILifetimeScope staticContainer;
   9:     private static object syncRoot = new object();
  10:     public AutofacContainerWithCustomModule()
  11:         : base(CreateContainer())
  12:     {
  14:     }
  15:     /// <summary>
  16:     /// This method creates the Autofac container and registers the custom type 
  17:     /// </summary>
  18:     /// <returns></returns>
  19:     private static ILifetimeScope CreateContainer()
  20:     {
  21:         if (staticContainer == null)
  22:         {
  23:             lock (syncRoot)
  24:             {
  25:                 if (staticContainer == null)
  26:                 {
  27:                     var builder = new ContainerBuilder();
  28:                     builder.RegisterModule<CustomAutofacModule>();
  29:                     staticContainer = builder.Build();
  30:                 }
  31:             }
  32:         }
  33:         return staticContainer.BeginLifetimeScope();
  34:     }
  35: }

This way, Chill will setup your Autofac registrations once. Very welcome if you’re registering expensive things such as NHibernate SessionFactories. It will also setup up two lifetime scopes. One per test run (since it’s a static singleton) and one child scope per test. This child scope can be customized to your hearts content.

Now if you wish to use this container, you can set the following attribute on class or assembly level:


Chill 2.0 beta released

I’ve just released a beta for Chill 2.0. What’s new?

  • Support for Integration testing using Autofac (no mocking).
  • Support for multiple Chill containers in a single assembly. Ideal if you want to have both integration tests and unit tests in a single assembly.
  • Support for automatic object mothers.
  • Chill is now also available as portable class library (thanks for that Dennis)!
  • Several usability tweaks.

Get the changes via Nuget:

Install-package Chill.Autofac –IncludePrerelease

Install-package Chill.AutofacNSubstitute –IncludePrerelease

Install-package Chill.AutofacFakeItEasy –IncludePrerelease

I’ll blog further about these improvements soon. As always feedback is very welcome.

Keep it Chill!