nest-automock

Overview

Overview of Automock Automock is a library designed to simplify unit testing in TypeScript applications, particularly useful in Nest.js. It automates the mocking of external dependencies for classes, reducing the manual effort needed to set up mocks in tests.

Key Points 1- Integration with Nest.js Dependency Injection (DI): - Nest.js uses a DI container that is crucial both for running applications and for testing. - In tests, mocking dependencies is essential for isolating components and testing them independently. - Automock streamlines this by providing a virtual container where dependencies are automatically mocked, eliminating the need for manual mock setup.

2- Installation of Automock: - Automock supports both Jest and Sinon testing frameworks. - You need to install Automock packages along with an adapter for Nest.js. - For Jest: bash npm i -D @automock/jest @automock/adapters.nestjs - For Sinon: bash npm i -D @automock/sinon @automock/adapters.nestjs

3- Example Usage with Jest: - Assume you have a CatsService class that depends on a Database class. - Normally, you'd manually mock the Database class when testing CatsService. - With Automock, you use TestBed from @automock/jest to automatically create mocks for the dependencies.

4- Test Setup:

• You create a test environment for CatsService using TestBed.create(CatsService).compile().
• unit gives you the instance of CatsService, and unitRef.get(Database) gives you a mocked instance of Database.
• You can set up mock responses and verify interactions in your tests.

5- Extended Example with Logger: - Adding a Logger class to CatsService demonstrates how Automock handles multiple dependencies. - In the test setup, you also mock the Logger dependency.

6- .mock().using() for Mock Implementations: - Automock provides a declarative way to specify mock implementations. - You define the mock behavior directly in the test setup, reducing the need for manual mocking in the test body.

7- Working with Dependency References: - unit and unitRef in the TestBed setup provide access to the class instance and its dependencies, respectively. - This setup allows for direct interaction with the class and its mocked dependencies.

8- Handling Different Providers: - Providers in Nest.js, like services or repositories, are essential for application functionality. - Automock supports string/symbol-based injection tokens, in line with Nest.js practices. - This allows for mocking dependencies that are provided using custom tokens.

Conclusion Automock simplifies the process of unit testing in Nest.js applications by automating the creation of mock objects for class dependencies. This allows developers to focus more on writing test cases rather than setting up mocks, leading to more efficient and robust unit testing. Automock works well with Jest and Sinon and integrates seamlessly with Nest.js's DI system, making it a valuable tool for testing in the Nest.js ecosystem.