Idealized testing-strategy model: many fast unit tests at the base, a layer of integration tests for components that can't be tested in isolation, and a thin top of end-to-end tests (expensive and flaky). The inverted 'ice-cream cone' flips the proportions and adds manual testing on top. Hasiński argues neither shape fits a typical Rails app, which is mostly integration tests because the app's logic is inseparable from the database.