ShimController.cs

public class SomeController : Controller
{
      public ActionResult GetCookie()
      {
            var cookie = this.Request.Cookies["CookieName"];
            
            if(cookie == null)
            {
                  return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            
            return this.RedirectToAction("index", "home");
      }
}

[TestClass]
public class SomeControllerTests
{
      [TestMethod]
      public void TestGetCookie()
      {
            var fakeRequest = new StubHttpRequestBase
            {
                  CookiesGet = () => new HttpCookieCollection
                  {
                        new HttpCookie("CookieName", "CookieValue");
                  }
            };
            
            var target = new SomeController();
            
            new ShimController(target)
            {
                  RequestGet = () => fakeRequest
            };
            
            var actual = target.GetCookie();
            
            Assert.IsInstanceOf(actual, typeof(HttpStatusCodeResult));
      }
}