What is the purpose of the Test Containers library in the application testing process?

Test Containers is a library for integration testing that allows running real application dependencies (such as databases, message brokers, cache systems) in isolated Docker containers during test execution. This helps create more reliable and reproducible tests, as tests interact with real services rather than mocks or stubs.

Example of usage: if the application works with PostgreSQL, Test Containers will launch a PostgreSQL container, and tests can interact with the real database, which improves testing quality and reduces the likelihood of errors related to environment mismatches.