I was able to use a SQLite in-memory database and avoid having to rebuild the schema for each test by using SQLite's support for 'Shared Cache', which allows an in-memory database to be shared across connections.
I did the following in AssemblyInitialize (I'm using MSTest):
Configure NHibernate (Fluently) to use SQLite with the following connection string:
FullUri=file:memorydb.db?mode=memory&cache=shared
Use that configuration to create a hbm2ddl.SchemaExport object, and execute it on a separate connection (but with that same connection string again).
- Leave that connection open, and referenced by a static field, until AssemblyCleanup, at which point it is closed and disposed of. This is because SQLite needs at least one active connection to be held on the in-memory database to know it's still required and avoid tidying up.
Before each test runs, a new session is created, and the test runs in a transaction which is rolled back at the end.
Here is an example of the test assembly-level code:
[TestClass]
public static class SampleAssemblySetup
{
private const string ConnectionString = "FullUri=file:memorydb.db?mode=memory&cache=shared";
private static SQLiteConnection _connection;
[AssemblyInitialize]
public static void AssemblyInit(TestContext context)
{
var configuration = Fluently.Configure()
.Database(SQLiteConfiguration.Standard.ConnectionString(ConnectionString))
.Mappings(m => m.FluentMappings.AddFromAssembly(Assembly.Load("MyMappingsAssembly")))
.ExposeConfiguration(x => x.SetProperty("current_session_context_class", "call"))
.BuildConfiguration();
// Create the schema in the database
// Because it's an in-memory database, we hold this connection open until all the tests are finished
var schemaExport = new SchemaExport(configuration);
_connection = new SQLiteConnection(ConnectionString);
_connection.Open();
schemaExport.Execute(false, true, false, _connection, null);
}
[AssemblyCleanup]
public static void AssemblyTearDown()
{
if (_connection != null)
{
_connection.Dispose();
_connection = null;
}
}
}
And a base class for each unit test class/fixture:
public class TestBase
{
[TestInitialize]
public virtual void Initialize()
{
NHibernateBootstrapper.InitializeSession();
var transaction = SessionFactory.Current.GetCurrentSession().BeginTransaction();
}
[TestCleanup]
public virtual void Cleanup()
{
var currentSession = SessionFactory.Current.GetCurrentSession();
if (currentSession.Transaction != null)
{
currentSession.Transaction.Rollback();
currentSession.Close();
}
NHibernateBootstrapper.CleanupSession();
}
}
Resource management could improve, I admit, but these are unit tests after all (suggested improvements welcome!).