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I want to fake an ObjectSet<T> from Entity Framework, has anyone done this at all? Specifically, I want to be able to fake the results that come back out of the query...

asked by bmains (13.2k points)

1 Answer

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Hi, we know of a limited solution for this problem.

Say you have a query like this:

IQueryable<Course> courseQuery =
                    from c in myLearningEntities.Courses
                    where c.CourseId == courseId
                    select c;

where Courses is an ObjectSet<Course>.

So you could fake the myLearnningEntites.Courses with a code that looks kind of like this:

var fakeEntities = Isolate.Fake.Instance<MyLearningEntities>();

var listOfCourses = new List<Course>();
var returnedCourse = new Course { CourseName = "NEO", CourseType = "Instructor-Led", IsMandatoryForEB = false };
Isolate.WhenCalled(() => fakeEntities.Courses).WillReturnCollectionValuesOf(listOfCourses.AsQueryable());

However, if you would try to use methods specific to ObjectSet and not to List, for example if you have a query like this:
IQueryable<Course> courseQuery =
                    from c in myLearningEntities.Courses.Include("CourseType")
                    where c.CourseId == courseId
                    select c;

Then the above test code would not work. You could write an exact WhenCalled chain on the whole lamda expression like so:
Isolate.WhenCalled(() => fakeEntities.Courses.Include("CourseType")).WillReturnCollectionValuesOf(listOfCourses.AsQueryable());

Does this apply to your case?
answered by yoel (1.9k points)