How to mock ObjectResult<T> generated from Entity Framework 6

[Steven T.]

Given:

MyDbContext.GetProjects() which is generated via EntityFramework 6 from a stored procedure.

The return type is ObjectResult<MyProject>

I want to mock the results with a specific collection of Data.

Mock.Arrange(() => MyDbContextMock.GetProjects()).Returns(FakeEmptyList());

trying to use the following:

public ObjectResult<MyProject> FakeEmptyList()
{
  return new ObjectResult<MyProject>();
}

results in:

Error 18 The type 'System.Data.Entity.Core.Objects.ObjectResult<T>' has no constructors defined ............

I am new to JustMock and appreciate the help.  Thanks!

[Kaloyan]

Hello Steven,

To fake an ObjectResult<T> you will need to use the ReturnsCollection method of JustMock. Let's assume the following code:

public class NerdDinners
{
    public ObjectResult<Dinner> Dinners { get; set; }
}

Now, to fake the return value of the above property we can use a simple list, like this:

public IList<Dinner> FakeDinners()
{
    return new List<Dinner>()
    {
        new Dinner()
        {
            DinnerID = 1,
            Title = "FakeDinner 1",
            EventDate = new DateTime(1222, 12, 12),
            Address = "Fake Address 1",
            HostedBy = "Fake Host 1"
        },
        new Dinner()
        {
            DinnerID = 2,
            Title = "FakeDinner 2",
            EventDate = new DateTime(1222, 12, 12),
            Address = "Fake Address 2",
            HostedBy = "Fake Host 2"
        },
        new Dinner()
        {
            DinnerID = 3,
            Title = "FakeDinner 3",
            EventDate = new DateTime(1222, 12, 12),
            Address = "Fake Address 3",
            HostedBy = "Fake Host 3"
        }
    };
}

And the actual test is as follows:

[TestMethod]
public void ShouldReturnFakeCollectionWhenExpected()
{
    // ARRANGE
    NerdDinners nerdDinners = new NerdDinners();

    Mock.Arrange(() => nerdDinners.Dinners).ReturnsCollection(FakeDinners());

    // ACT
    var actualQuery = nerdDinners.Dinners;

    // ASSERT
    Assert.AreEqual(3, actualQuery.Count());
}

Please, note the usage of the ReturnsCollection method. It dynamically converts the List of Dinners and allows you to arrange it as a return value of an ObjectResult type. More about this can be found here and here.

I hope this helps. Please, let me know if there is anything else I can help you with.

Regards,
Kaloyan
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