In this section, you will learn how to structure your tests using Jest so that they are clear, maintainable, and effective. Jest provides a simple yet powerful structure for organizing your tests, making use of describe blocks, individual tests (test or it), and assertions (expect).

Organizing Tests with describe

The describe block allows you to group related tests under a common context. This makes your test suite more organized and easier to read.

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Writing Tests with test or it

Within a describe block, we use test or it to define individual tests. These methods are interchangeable, and the choice between them is a matter of personal or team style preference.

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Assertions with expect

Assertions are the core of tests in Jest. We use expect to evaluate the result of an expression or function and verify if it meets a specific condition.

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Test Lifecycle

Jest allows defining hooks to set up and tear down the environment before and after tests. The most common hooks are:

• beforeAll: Runs once before all tests in the block.
• afterAll: Runs once after all tests in the block.
• beforeEach: Runs before each test in the block.
• afterEach: Runs after each test in the block.

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Complete Example

Below is an example that uses all the mentioned concepts:

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[Placeholder for image: Diagram showing the structure of a test in Jest with describe blocks, it/test, beforeAll/afterAll/ beforeEach/afterEach hooks, and expect assertions.]

Conclusion

The key to writing good tests is organization and clarity. Using describe, test or it, and expect effectively will help you keep your tests readable and easy to understand. In the next section, we will explore more details on how to use assertions and matchers in Jest.