isabella232 / justmock.entityframework

In-memory mock DbSet and DbContext mocking amenities for JustMock.

Telerik.JustMock.EntityFramework

In-memory mock DbSet and DbContext mocking amenities for JustMock.

Getting Started

Install the package from NuGet: https://www.nuget.org/packages/JustMock.EntityFramework

Mocking DbContext

Here is an example straight from the tests:

[TestClass]
public class DbContextTests
{
	public class Person
	{
		public int Id { get; set; }
		public string Name { get; set; }
	}

	public class DbContextOne : DbContext
	{
		public DbSet<Person> People { get; set; }
	}

	[TestMethod]
	public void Prepare_ShouldAssignDbSetProperties()
	{
		var dbContext = EntityFrameworkMock.Create<DbContextOne>();
		Assert.IsNotNull(dbContext.People);
	}
}

In the above example I create a mock of my DbContext-deriving class. As a result, all fields that are of type DbSet<T> or IDbSet<T> are automatically populated with a mock in-memory DbSet (initially empty).

We can also create a mock from a DbContext-like interface, like in the example below:

public interface IMyDbContext
{
	IDbSet<Person> People { get; }
}

[TestMethod]
public void Prepare_Interface_DbSetsInitialized()
{
	var dbContext = EntityFrameworkMock.Create<IMyDbContext>();
	Assert.IsNotNull(dbContext.People);
}

Populating data

Populating the context with data lets you simulate a database that has data in it. Here's how we can populate our context:

[TestMethod]
public async Task Bind_BindData_DataIsThere()
{
	var ctx = Mock.Create<TheDbContext>().PrepareMock();

	var list = new List<Person>
	{
		new Person { Id = 1, Name = "a" }
	};

	ctx.People.Bind(list);

	var data = await ctx.People.ToListAsync();
	Assert.AreSame(list[0], data[0]);
}

The Bind() extension method binds a DbSet or IDbSet on the mock context to a backing collection, which can be anything, but it's best to use a ObservableCollection<T> (Local works only when the backing collection is itself observable).

Changes made to the DbSet are passed to the backing collection and vice versa.

Further reading

Check out the unit tests in Telerik.JustMock.EntityFramework.Tests - they double as example usage.