Click here for an example implementation.
A common setup in when developing locally is to have a "working" database that you use for development, and a "test" database that you use for running tests.
Running tests typically looks like this:
- Run migrations to set up the "test" database to get the database up to date.
- Run tests sequentially, each time cleaning up the database before/after runs.
The test suite gets slower over time as more tests are added, since they're run sequentially in order to avoid conflicts with the test database between tests. You can get by with using mocks or setting up your tests in a way that don't conflict with each other, but the downsides are that your tests can be unrealistic or brittle based on how you set up the data.
A solution to this is to configure the test suite so that tests are able to run in parallel. It's a bit more work, but it can greatly speed up the test suite.
The idea is to create a new database per test file, run migrations, and clean it up afterward.