What is the testing pyramid and what are its benefits? Have you applied the pyramid in practice?

The testing pyramid is a concept that describes the optimal ratio of different types of tests in a project:

• Unit tests (at the code level) — many, fast, isolated, cover logic.
• Integration tests — fewer, check interaction between components.
• E2E (end-to-end) tests — even fewer, test the entire system from the user's perspective.

Advantages of the pyramid:

• Fast execution and feedback due to a large number of unit tests.
• Reliability and stability of tests, as unit tests are simpler and less fragile.
• Saving time and resources, as E2E tests are slow and complex.

In practice, applying the pyramid helps maintain a balance between coverage and testing costs. For example, in a project, I saw how increasing the share of unit tests reduced the number of bugs at the integration level and sped up development, while E2E tests were used only for critical scenarios.