Unit testing is built-in testing provided as an integral part of Laravel. It consists of unit tests which detect and prevent regressions in the framework. Unit tests can be run through the available artisan command-line utility.

In the context of Laravel, unit testing refers to the practice of testing individual units or components of your codebase in isolation to ensure they behave as expected. These units could be methods, functions, classes, or even smaller parts of your code. Unit tests are typically automated and focus on verifying that each unit of code performs its intended functionality correctly.

Key aspects of unit testing in Laravel include:

Isolation: Unit tests should isolate the code being tested from its dependencies. In Laravel, this often involves using mocking or dependency injection to simulate the behavior of external dependencies.
Speed: Unit tests should be fast to execute, allowing developers to run them frequently during development without significant overhead.
Determinism: Unit tests should produce consistent results regardless of when or where they are run. This ensures reliability and repeatability in the testing process.
Coverage: Unit tests should aim to cover all critical paths and edge cases within the unit of code being tested, providing confidence in its correctness.

When asked about unit testing in a Laravel interview, it’s essential to demonstrate an understanding of these principles and how they apply within the Laravel framework. Additionally, mentioning Laravel’s built-in testing facilities, such as PHPUnit and Laravel’s testing helpers, would be beneficial.