Entity framework 6 mocking include method on dbset


Question

Have been googling for a solution to the problem on how to mock the include method on dbset in EF6. The problem is well documented here :-

http://entityframework.codeplex.com/discussions/461731

Unfortunately though there does not seem to be a valid solution in there.

Has anyone found a workaround to this?

I do understand that we shouldn't really be mocking the EF6 context, but the project lead has insisted on it.

Thanks in advance.

Accepted Answer

So, this is possible if a bit of a faff!

In the below I setup the mock context and sets and can call include successfully. I think that the secret sauce is in stubbing the calls through to Provider, Expression and GetEnumerator and in setting the DbSet properties on the stubbed context to the stubbed sets and not stubbing the context to returning them.

A runnable example is available on GitHub

    [Test]
    public void CanUseIncludeWithMocks()
    {
        var child = new Child();
        var parent = new Parent();
        parent.Children.Add(child);

        var parents = new List<Parent>
            {
                parent
            }.AsQueryable();

        var children = new List<Child>
            {
                child
            }.AsQueryable();

        var mockContext = MockRepository.GenerateStub<TestContext>();

        var mockParentSet = MockRepository.GenerateStub<IDbSet<Parent>>();
        var mockChildSet = MockRepository.GenerateStub<IDbSet<Child>>();

        mockParentSet.Stub(m => m.Provider).Return(parents.Provider);
        mockParentSet.Stub(m => m.Expression).Return(parents.Expression);
        mockParentSet.Stub(m => m.GetEnumerator()).Return(parents.GetEnumerator());

        mockChildSet.Stub(m => m.Provider).Return(children.Provider);
        mockChildSet.Stub(m => m.Expression).Return(children.Expression);
        mockChildSet.Stub(m => m.GetEnumerator()).Return(children.GetEnumerator());

        mockContext.Parents = mockParentSet;
        mockContext.Children = mockChildSet;

        mockContext.Parents.Should().HaveCount(1);
        mockContext.Children.Should().HaveCount(1);

        mockContext.Parents.First().Children.FirstOrDefault().Should().NotBeNull();

        var query = mockContext.Parents.Include(p=>p.Children).Select(pc => pc);

        query.Should().NotBeNull().And.HaveCount(1);
        query.First().Children.Should().NotBeEmpty().And.HaveCount(1);

    }

Popular Answer

I had the same drama as @GetFuzzy above - it seemed that no matter what I did I couldn't avoid the NullReferenceException whenever an Include() call was made on a Moq DbSet. The Github example in the other answer unfortunately did not work: Set.Include() always returns null.

After fiddling for a while I came up with a workaround for this.

[Test]
public void CanUseIncludeWithMocks()
{
    var child = new Child();
    var parent = new Parent();
    parent.Children.Add(child);

    var parents = new List<Parent> { parent };
    var children = new List<Child> { child };

    var parentsDbSet1 = new FakeDbSet<Parent>();
    parentsDbSet1.SetData(parents);

    var parentsDbSet2 = new FakeDbSet<Parent>();
    parentsDbSet2.SetData(parents);

    parentsDbSet1.Setup(x => x.Include(It.IsAny<string>())).Returns(parentsDbSet2.Object);

    // Can now test a method that does something like: context.Set<Parent>().Include("Children") etc
}


public class FakeDbSet<T> : Mock<DbSet<T>> where T : class
{
    public void SetData(IEnumerable<T> data)
    {
        var mockDataQueryable = data.AsQueryable();

        As<IQueryable<T>>().Setup(x => x.Provider).Returns(mockDataQueryable.Provider);
        As<IQueryable<T>>().Setup(x => x.Expression).Returns(mockDataQueryable.Expression);
        As<IQueryable<T>>().Setup(x => x.ElementType).Returns(mockDataQueryable.ElementType);
        As<IQueryable<T>>().Setup(x => x.GetEnumerator()).Returns(mockDataQueryable.GetEnumerator());
    }
}

I really don't like the clumsiness of having to have two fake DbSets but for some reason this doesn't work:

parentsDbSet1.Setup(x => x.Include(It.IsAny<string>())).Returns(parentsDbSet1.Object);

anyone have an explanation for this?





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