In ModelTests we use RollbackContext to register undo actions for cleaning leftovers. The general principle for using RollbackContext is that we should register an undo action right after the successful allocation of a resource, otherwise we leave a window between the resource allocation and cleanup action registration. If it happened to raise an exception in this window, the allocated resource is not cleaned. In ModelTests, you can find that some test methods is not properly using RollbackContext, they place assertions between resource allocation and cleanup registration. This patch tries to adjust the order peroperly.