To test Elixir applications, use the built-in ExUnit framework, which provides tools for writing unit, integration, and property-based tests. Structure your tests for clarity and maintainability.

Testing is a vital aspect of Elixir development, and the built-in ExUnit framework provides comprehensive tools for writing and executing tests effectively. ExUnit allows you to define unit tests, integration tests, and even property-based tests to ensure the reliability and correctness of your applications. When writing tests, it's essential to structure them clearly, typically by organizing them into separate modules that reflect the functionality being tested. Each test case should focus on a specific aspect of your code, using descriptive names to convey its purpose. To run your tests, use the mix test command, which will execute all test files in the test directory. ExUnit also provides useful assertions, such as assert, refute, and custom assertions to validate expected outcomes. For more complex scenarios, you can use mocking libraries like Mox to simulate dependencies and isolate the unit of work being tested. Additionally, consider writing property-based tests using libraries like PropCheck, which can help identify edge cases by testing a wide range of inputs automatically. By adopting a thorough testing strategy with ExUnit, you can ensure that your Elixir applications are robust, maintainable, and resilient to change.