Unit testing in .NET is pretty nice when your dependency injection/IoC is set up well, but Entity Framework 6 isn’t the nicest framework for mocking and testing. If you’re using ASP.NET MVC 5, you may have run into this scenario.
Problem: You want to use or mock a DbSet
So you have an IEnumerable (list, array, etc) that you want to use on your tests, but your DbContext only has DbSets. Unfortunately, the DbSet constructor is protected, so you can’t just ‘new’ one up. The solution is our friend Moq.
Solution
This handy IEnumerable extension will give you back a DBSet with your IEnumerable in the data. Now you can mock out your DbContext properties or result sets however you wish! You probably want to leave callBase as true to the base implementation is called when you haven’t set up certain properties, but if you’re having problems, maybe try setting callBase to false.
public static class TestingExtensions
{
private static Mock<DbSet<T>> AsMockDbSet<T>(IEnumerable<T> data, bool callBase = true) where T : class
{
var mockSet = new Mock<DbSet<T>>();
var queryable = data.AsQueryable();
mockSet.As<IQueryable<T>>().Setup(m => m.Provider).Returns(queryable.Provider);
mockSet.As<IQueryable<T>>().Setup(m => m.Expression).Returns(queryable.Expression);
mockSet.As<IQueryable<T>>().Setup(m => m.ElementType).Returns(queryable.ElementType);
mockSet.As<IQueryable<T>>().Setup(m => m.GetEnumerator()).Returns(queryable.GetEnumerator());
mockSet.CallBase = callBase;
return mockSet;
}
}
