Mocking IHttpRequestContext for Unit Testing

HttpSessionStateTests.cs

        [TestFixture]
        public class when_removing_a_coupon
        {
            [Test]
            public void then_should_remove_the_coupon_from_the_session()
            {
                // Arrange
                var httpSessionStateBase = new Mock<HttpSessionStateBase>();
                var coupons = new Dictionary<int, Coupon>();
                httpSessionStateBase.SetupGet(session => session["PendingBuyerCoupons"])
                    .Returns(buyerCoupons);

                var httpRequestContext = new Mock<IHttpRequestContext>();
                httpRequestContext.SetupGet(context => context.Session).Returns(httpSessionStateBase.Object);

                var service = new SessionDataService(httpRequestContext.Object);

                var coupon = new Coupon {DigitalCouponId = 1};
                service.AddCoupon(coupon);

                // Act
                service.RemoveCoupon(coupon);

                // Assert
                Assert.That(coupons.Count, Is.EqualTo(0));   
            }
        }