Writing automated tests for data migrations

Question

Is there a straightforward way to unit test data migrations in Django?

Let's say I have a CharField with fixed choices like London and Tokio, but I want to replace the enum with a foreign key to a dedicated model so that I can store additional information about each city (e.g. the country).

My approach to writing the migration would be:

• Add nullable ForeignKey field
• Perform data migration that inserts a value into the ForeignKey field that reflects the value of the CharField
• Make the ForeignKey non-nullable
• Remove the CharField

But how would you test this with TestCase?

Answer 1

It's surely doable. I think you could make use of the tools Django tests itself with: MigrationExecutor and MigrationTestBase. Here's a sample of how to invoke migrations in your tests.