Testing Ninject container

I've found really useful to test our IoC container to make sure that all the components that are registered can be resolved.

This is the way I usually test my Ninject container

The model

so let's say that we have the following model:

public interface ICommand { }

public interface ICommandHandler<in T> where T : ICommand
{
    void Handle(T command);
}

public class DeploySqlScriptsUsingAGlobalTransactionCommand : ICommand
{
    public DeploySqlScriptsUsingAGlobalTransactionCommand(IEnumerable<string> scripts)
    {
        Scripts = scripts;
    }

    public IEnumerable<string> Scripts { get; private set; }
}

public class DeploySqlScriptsUsingAGlobalTransactionCommandHandler :
    ICommandHandler<DeploySqlScriptsUsingAGlobalTransactionCommand>
{
    private readonly IScriptDeployerService _scriptDeployerService;

    public DeploySqlScriptsUsingAGlobalTransactionCommandHandler(IScriptDeployerService scriptDeployerService)
    {
        _scriptDeployerService = scriptDeployerService;
    }

    public void Handle(DeploySqlScriptsUsingAGlobalTransactionCommand command)
    {
        //shalalalalal
        command.Scripts.ToList().ForEach(_scriptDeployerService.Deploy);
        Console.WriteLine("Scripts deployed");
    }
}

public interface IScriptDeployerService
{
    void Deploy(string script);
}

Note that we don't have a concrete implementation of IScriptDeployerService

The test

So we create this test to make sure that the container is valid:

[TestMethod]
public void it_should_resolve_all_registered_components_in_the_container()
{
    #region Binding container

    var kernel = new StandardKernel();

    kernel.Bind(config =>
    {
        config.FromThisAssembly()
            .SelectAllClasses()
            .BindAllInterfaces();
    });

    ServiceLocator.SetLocatorProvider(() => new NinjectServiceLocator(kernel));

    kernel.Bind<IServiceLocator>().ToConstant(ServiceLocator.Current); 

    #endregion

    #region Testing container

    var field = typeof (KernelBase).GetField("bindings",
        BindingFlags.Instance | BindingFlags.NonPublic);

    field.Should().NotBeNull();

    var bindingsMap = field.GetValue(kernel) as Multimap<Type, IBinding>;

    bindingsMap.Should().NotBeNull();
    bindingsMap.Should().NotBeEmpty();

    var locator = ServiceLocator.Current.GetInstance<IServiceLocator>();

    locator.Should().NotBeNull();

    bindingsMap.SelectMany(x => x.Value).ToList()
        .ForEach(binding => ServiceLocator.Current.Invoking(instance =>
        {
            var services = instance.GetAllInstances(binding.Service);

            services.Count().Should().BeGreaterOrEqualTo(1);

            if (services.Count() == 1)
            {
                instance.GetInstance(binding.Service);
            }
        }).ShouldNotThrow());

    #endregion
}

The error

When we run the test we receive the following error from Ninject:

Result Message: Did not expect any exception, but found Ninject.ActivationException with message "Error activating IScriptDeployerService No matching bindings are available, and the type is not self-bindable. Activation path: 2) Injection of dependency IScriptDeployerService into parameter scriptDeployerService of constructor of type DeploySqlScriptsUsingAGlobalTransactionCommandHandler 1) Request for ICommandHandler{DeploySqlScriptsUsingAGlobalTransactionCommand}

Very explicit

The fix

So now let's fix it:

Let's add the missing concrete implementation:

public class ScriptDeployerService : IScriptDeployerService
{
    public void Deploy(string script)
    {
        Console.WriteLine("Script deployed: {0}", script);
    }
}

The result

And now our test pass =) Awesome