Repository Pattern and unit testing from memory

Question

I have seen some implementations of the Repository Pattern, very simple and intuitive, linked form other answers here in stackoverflow

http://www.codeproject.com/Tips/30

Answer 1

I'd suggest to use a mocking library like Moq or RhinoMocks. A nice tutorial using Moq can be found here.

Before you decide which one you'll use, the followings might help:

• http://graemef.com/blog/2011/02/10/A-quick-comparison-of-some-.NET-mocking-frameworks/

• http://jimmykeen.net/articles/09-jul-2012/mocking-frameworks-comparison-part-1-introduction

Additional information : Comparison of unit test framework can be found here.

---

UPDATE following OP's request

Create a in memory database

var bookInMemoryDatabase = new List
{
    new Book() {Id = 1, Name = "Book1"},
    new Book() {Id = 2, Name = "Book2"},
    new Book() {Id = 3, Name = "Book3"}
};

Mock your repository (I used Moq for the following example)

var repository = new Mock>();

Set up your repository

// When I call GetById method defined in my IRepository contract, the moq will try to find
// matching element in my memory database and return it.

repository.Setup(x => x.GetById(It.IsAny()))
          .Returns((int i) => bookInMemoryDatabase.Single(bo => bo.Id == i));

Create a library object by passing your mock object in constructor parameter

var library = new Library(repository.Object);

And finally some tests :

// First scenario look up for some book that really exists 
var bookThatExists = library.GetByID(3);
Assert.IsNotNull(bookThatExists);
Assert.AreEqual(bookThatExists.Id, 3);
Assert.AreEqual(bookThatExists.Name, "Book3");

// Second scenario look for some book that does not exist 
//(I don't have any book in my memory database with Id = 5 

Assert.That(() => library.GetByID(5),
                   Throws.Exception
                         .TypeOf());

// Add more test case depending on your business context
.....