Recreate and Reseed LocalDb Before Each Unit Test

Question

I\'m attempting to write unit/integration tests for my ASP.NET Web API project and struggling to run each test in isolation. Allow me to explain.

I have a *.testset

Answer 1

Here's what I ended up doing for anyone that is interested.

I extended DropCreateDatabaseAlways<TContext> and overrode the Seed method to populate my database with known test data that my unit tests can rely on.

public class MyDatabaseInitializer : System.Data.Entity.DropCreateDatabaseAlways<MyDbContext>
{
    protected override void Seed(MyDbContext context)
    {
        // Add entities to database.

        context.SaveChanges();
    }
}

I then implemented an [AssemblyInitialize] method which sets the database initializer.

[TestClass]
public class Global
{
    [AssemblyInitialize]
    public static void AssemblyInitialize(TestContext context)
    {
        System.Data.Entity.Database.SetInitializer(new MyDatabaseInitializer());
    }
}

This sets the initializer for the database but does not actually run it. The intitializer is run in a [TestInitialize] method I wrote which forces the database to be dropped, recreated and reseeded before each test.

[TestClass]
public class MyTestClass
{
    [TestInitialize]
    public void TestInitialize()
    {
        MyDbContext context = new MyDbContext();
        context.Database.Initialize(true);
    }

    [TestMethod]
    public void MyUnitTest()
    {
        Assert.IsTrue(true);
    }
}

Answer 2

I would suggest re-creating your database before you begin your tests and then wrap each in a transaction that always rolls back. This is quite beneficial if your recreate stage takes a lot of time to complete (e.g. because of the actions that need to be performed, etc.).

Answer 3

In our current setup we're recreating the database schema before each class is loaded (with ClassInitialize attribute, but this could definitely be moved to AssemblyInitialize), and just seeding/cleaning up the database with the appropriate records before/after each test run (with TestInitialize/TestCleanup attribute).

More info: http://msdn.microsoft.com/en-us/library/ms379625(v=vs.80).aspx