How do you mock adding items to a repository or DbContext using moq?

Question

The examples I\'ve seen for using moq for a repository only show how to mock things being returned. I have a somewhat strange requirement: when a query is executed, if a conditi

Answer 1

Times have changed -- since the release of Entity Framework 6 it has become much easier to mock database context and datasets. This article outlines the particulars.

Testing non-query scenarios

using Microsoft.VisualStudio.TestTools.UnitTesting; 
using Moq; 
using System.Data.Entity; 

namespace TestingDemo 
{ 
    [TestClass] 
    public class NonQueryTests 
    { 
        [TestMethod] 
        public void CreateBlog_saves_a_blog_via_context() 
        { 
            var mockSet = new Mock>(); 

            var mockContext = new Mock(); 
            mockContext.Setup(m => m.Blogs).Returns(mockSet.Object); 

            var service = new BlogService(mockContext.Object); 
            service.AddBlog("ADO.NET Blog", "http://blogs.msdn.com/adonet"); 

            mockSet.Verify(m => m.Add(It.IsAny()), Times.Once()); 
            mockContext.Verify(m => m.SaveChanges(), Times.Once()); 
        } 
    } 
}

Testing query scenarios Query testing is pretty sweet now, because you can build up test data sets in code and then execute your tests against them:

using Microsoft.VisualStudio.TestTools.UnitTesting; 
using Moq; 
using System.Collections.Generic; 
using System.Data.Entity; 
using System.Linq; 

namespace TestingDemo 
{ 
    [TestClass] 
    public class QueryTests 
    { 
        [TestMethod] 
        public void GetAllBlogs_orders_by_name() 
        { 
            var data = new List 
            { 
                new Blog { Name = "BBB" }, 
                new Blog { Name = "ZZZ" }, 
                new Blog { Name = "AAA" }, 
            }.AsQueryable(); 

            var mockSet = new Mock>(); 
            mockSet.As>().Setup(m => m.Provider).Returns(data.Provider); 
            mockSet.As>().Setup(m => m.Expression).Returns(data.Expression); 
            mockSet.As>().Setup(m => m.ElementType).Returns(data.ElementType); 
            mockSet.As>().Setup(m => m.GetEnumerator()).Returns(0 => data.GetEnumerator()); 

            var mockContext = new Mock(); 
            mockContext.Setup(c => c.Blogs).Returns(mockSet.Object); 

            var service = new BlogService(mockContext.Object); 
            var blogs = service.GetAllBlogs(); 

            Assert.AreEqual(3, blogs.Count); 
            Assert.AreEqual("AAA", blogs[0].Name); 
            Assert.AreEqual("BBB", blogs[1].Name); 
            Assert.AreEqual("ZZZ", blogs[2].Name); 
        } 
    } 
}