How to test use of DI (NInject)

Question

I have an ASP.NET MVC app that has a NInject container for dependency injection. As advertised, IoC makes it pretty easy for me to test components in isolation, and then easy to compose components in the application.

I want to test my use of the DI. I don't want to test that the DI component operates correctly. I trust that the NInject folks do that pretty well. I want to test that I have used the DI to compose components correctly with respect to my application's intentions. I don't want to test NInject, I want to test my use of NInject. (I also don't want to try to categorize this as a unit test or an integration test. I only want to be able to, sometime before I get to production, demonstrate why I have confidence that my particular use of NInject works.)

Suppose I have something like:

    private static void RegisterDatabaseConnections(IBindingRoot kernel)
    {
        string connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
        kernel.Bind<IProvideDbConnections>()
            .To<Connector>()
            .WhenInjectedInto<ActivityStore>()
            .WithConstructorArgument("connectionString", connectionString);
        kernel.Bind<IProvideDbConnections>()
            .To<Connector>()
            .WhenInjectedInto<CrConnector>()
            .WithConstructorArgument("connectionString", connectionString);
        kernel.Bind<IProvideDbConnections>()
            .To<CrConnector>()
        ...
    }

Somewhere I have:

    public class Writer
    {
        public Writer(IProvideDBConnections connector)
        {
            Connector = connector;
        }
        private IProvideDBConnections Connector { get; set; }
        ....
    }

I would like to write an MSTest like

    [TestMethod]
    public void TestThatWriterCrConnectorContainsConnector()
    {
        ...
    }

so that I can verify that I wrote RegisterDatabaseConnections to give me what I expect. I am having trouble getting started down that path, because I don't know to access a kernel to set up any tests. The code that starts the kernel in the application is a collection of static private methods, and is a little mysterious to me, and I don't see how I would do this in the context of a test. Any help?

Answer 1

I would create my own kernel and Load() the module(s) you are wanting to test.

[TestMethod]
public void TestThatWriterCrConnectorContainsConnector()
{
    var kernel = new StandardKernel();
    kernel.Load(new ModuleA(), new ModuleB());

    var obj = kernel.Get<Writer>();
    // ... assert
}

this is assuming you have defined all your bindings that you want to test in a NinjectModule