ObjectContext never derives from an interface?? How do you apply DI/IoC in case of multiple types of ObjectContext?

Question

If you have a system that has multiple types of object contexts. For Eg: BillingObjectContext, HumanResourceObjectContext etc. All derive from ObjectContext but ObjectContex

Answer 1

If you must depend on it in a test, you have to mock it. Here's a sample; it's not much harder than implementing an interface. See also TDD improvements in EF 4.

Answer 2

Why can't we just create the actual context object to be used in our tests? Since we don't want our tests to affect the production database, we can always specify a connection string that points to a test database. Before running each test, construct a new context, add the data you will need in your test, proceed with the unit test, then in the test cleanup section, delete all the records that were created during the test. The only side-affect here would be that the auto-increment IDs would be used up in the test database, but since it's a test database - who cares?

I know that most answers regarding this question propose using DI/IoC designs to create interfaces for data contexts etc. but the reason I am using Entity Framework is exactly to not write any interfaces for my database connections, object models, and simple CRUD transactions. To write mock interfaces for my data objects and to write complex queryable objects to support LINQ, defeats the purpose of relying on highly-tested and reliable Entity Framework.

This pattern for unit testing is not new - Ruby on Rails has been using it for a long time and it's worked out great. Just as .NET provides EF, RoR provides ActiveRecord objects and each unit test creates the objects it needs, proceeds with the tests, and then deletes all the constructed records.

How to specify connection string for test environment? Since all tests are in their own dedicated test project, adding a new App.Config file with a connection string for the test database would suffice.

Just think of how much headache and pain this will save you.

namespace ProjectNamespace
{
    [TestClass]
    public class UnitTest1
    {
        private ObjectContext objContext;

        [TestInitialize]
        public void SetUp()
        {
            // Create the object context and add all the necessary data records.
        }

        [TestMethod]
        public void TestMethod1()
        {
            // Runs the tests. 
        }

        [TestCleanup]
        public void CleanUp()
        {
            // Delete created records. 
        }
    }
}