Skip to main content

Fast Database Resets

To reset the database between each unit test, Joist's joist-codegen command generates a flush_database stored procedure [^1] that will delete all rows/reset the sequence ids:

await knex.select(knex.raw("flush_database()"));

This is generated at the end of the joist-codegen, which should only be invoked against local development databases, i.e. this function should never exist in your production database. It is only for local testing.

Your test suite should invoke this knex.select command in a suite-test beforeEach.

What About Per-Test Transactions?​

As an alternative to Joist's flush_database approach, some ORMs invoke tests in a transaction, and then rollback the transaction before the next test (i.e. Rails does this).

However, this has a few downsides:

  1. Debugging failed tests is more difficult b/c the data you want to investigate via psql has disappeared/been rolled back, and
  2. Your tests cannot test any behavior that uses transactions.

For this reasons, Joist prefers the flush_database approach, however you could still use the transaction-per-test approach by putting BEGIN and ROLLBACK commands in your project's beforeEach/afterEach.

[^1] flush_database is the only stored procedure that Joist uses, and opting for a stored procedure is solely an optimization (1 SQL statement to reset all tables) to keep tests as fast as possible.