beginner-testing

Use pytest with Flask's test client to visit routes and assert on responses. Create a test file, call app.test_client().get('/') and assert the status code equals 200, then run pytest from the command line.

Use minitest with rack-test by including Rack::Test::Methods in your test class and defining an app method returning Sinatra::Application. Then call get or post helpers and assert on last_response.ok? or response body content.

RED means writing a failing test for a feature that does not exist yet. GREEN means writing the minimum code to make that test pass. REFACTOR means cleaning up the code while keeping all tests passing.

Start with route tests that verify pages return status 200 instead of 404. Then test form submissions, database saves, and that data displays correctly, leaving edge cases and error handling for later.

A 404 in a test means the route does not exist in your application yet. In TDD this is the expected RED phase, so write the route handler in your app and rerun the test to reach GREEN.