Mocking HttpContext.Session in .NET Core

Question

I'm using xUnit with Moq to write unit tests for my app. However, I'm having a hard time to mock the session.

The system under test is a controller action, the method under test uses a TempData["UserMessage"] which always is null as Session isn't initialized.

This is a printscreen of how I'm trying to mock the dependency.

Error thrown is at line 65 and is following

Controllers should be dumb, you should instead have a service and test those. — David Pine
– David Pine, Commented Oct 10, 2016 at 20:50
I do have services where I store my logic. You mean one shouldn't test it at all? My intent was to test if it returned correct usermessage upon error/correct values sent in. — Rovdjuret
– Rovdjuret, Commented Oct 10, 2016 at 20:52
You're just testing that the framework does its thing, I usually try to avoid that. — David Pine
– David Pine, Commented Oct 10, 2016 at 20:53
I'm trying to digest what you are writing, but I can't see why I shouldn't test that our actions does various service method calls in correct order etc. Do you have any link to what you are suggesting? I'm really interested in how thin/stupid they should be. — Rovdjuret
– Rovdjuret, Commented Oct 10, 2016 at 21:03

David Pine · Accepted Answer · 2016-10-11 02:32:23Z

1

A general rule of thumb is to avoid having "fat controllers". My controllers literally have the model or arguments they need to execute against a corresponding service. Ideally, your controller actions are a single call with a lot of attributes that describe the endpoint, consider the following:

public class MyThinController : Controller
{
    [
        HttpGet,
        Route("api/[controller]/foos/{bar}"),
        Authorize(Policy = nameof(Policies.StackoverflowOp))
    ]
    public Task<IActionResult> GetFoo([FromRoute] Bar bar,
                                      [FromServices] IExampleService service)
        => service.GetAsync(bar);
}

Then, your only concern should be that given a bar the implementation of IExampleService does correctly get a Foo.

But if you're completely not willing to do it the correct way, there is always a way to do it the wrong way. You're actually looking for the ActionContext.HttpContext which is moq-ready.

answered Oct 11, 2016 at 2:32

David Pine

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1 Comment

Rovdjuret Over a year ago

Thanks David, this is makes a lot of sense :)

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