Overview

Vitest-when is a powerful extension for Vitest that provides a more structured and readable way to manage mock functions in your tests. By simplifying the process of creating stubs—fake objects with predefined responses—this library ensures that your testing experience remains efficient and less error-prone. Drawing inspiration from well-known libraries like testdouble.js and jest-when, Vitest-when helps eliminate the complexities that often accompany mock setups, making it easier to write and maintain tests, especially for those using TypeScript.

With vitest-when, you can achieve clear and concise test setups that significantly reduce the likelihood of misconfiguration. It streamlines the arrangements of your assertions, allowing developers to focus on what truly matters: ensuring that the code behaves as expected.

Features

Readable Syntax: The API is designed to be intuitive, making it easy to understand and use, even for those new to testing.
Pre-configured Responses: Easily create stubs that return values, resolve promises, throw errors, or trigger functions based on matching arguments.
Type Safety: Fully type-checked configuration helps prevent errors associated with incorrectly set up mocks.
Focused Test Arrangement: All stub configurations occur during the "arrange" phase, improving the readability of your tests and reducing cognitive load.
Customizable Behavior: Options such as ignoreExtraArgs and times allow for flexible control over how and when your stubs operate.
Reset Functionality: Use vi.resetAllMocks() or set mockReset to true for easy cleanup after tests, ensuring no accidental state carries over.
Asymmetric Matchers: Support for Vitest's asymmetric matchers enables more complex matching criteria while keeping your test setup clean and simple.
Easy Integration: Seamlessly wrap existing mock functions from vi.fn() or vi.spyOn(), allowing you to enhance your existing Vitest mocks with minimal effort.

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Vitest When