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

You can do this by mocking the DbSet.Add() method, like so:

[Fact]
public void CreateBlog_saves_a_blog_via_context()
{
  var data = new List
  {
    new Blog { Name = "BBB" },
    new Blog { Name = "ZZZ" },
    new Blog { Name = "AAA" },
  };
  
  var mockSet = new Mock>();
  mockSet.Setup(blogs => blogs.Add(It.IsAny)).Returns(blog =>
  {
    data.Add(blog);
    return blog;
  });
  
  var mockContext = new Mock();
  mockContext.Setup(m => m.Blogs).Returns(mockSet.Object);
  
  var service = new BlogService(mockContext.Object);
  var blog = service.AddBlog("_ADO.NET Blog", "http://blogs.msdn.com/adonet");
  var blogs = service.GetAllBlogs();
  
  mockSet.Verify(m => m.Add(It.IsAny()), Times.Once());
  mockContext.Verify(m => m.SaveChanges(), Times.Once());
  
  Assert.NotNull(blog)
  Assert.Equal(4, blogs.Count);
  Assert.Equal("AAA", blogs(1).Name);
  Assert.Equal("BBB", blogs(2).Name);
  Assert.Equal("ZZZ", blogs(3).Name);
}

This is adapted from the documentation found here.