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Jest BeforeEach vs BeforeAll: Which One Should You Use?

When writing tests with Jest, you’ll often need to use one or more of the [built-in test lifecycle methods](https://jestjs.io/docs/en/apitest-lifecycle-methods). These methods allow you to run code before or after each test, or before or after all tests in a suite.

In this article, we’ll compare the `beforeEach` and `beforeAll` methods, and discuss when you should use each one. We’ll also provide some code examples to help you understand how these methods work.

beforeEach vs beforeAll

The `beforeEach` method runs before each test in a test suite. This means that the code in the `beforeEach` block will be executed before each test is run.

The `beforeAll` method runs before all tests in a test suite. This means that the code in the `beforeAll` block will be executed only once, before any of the tests are run.

When to use beforeEach vs beforeAll

So, when should you use `beforeEach` and when should you use `beforeAll`? Here are a few guidelines:

Use `beforeEach` to set up any state that you need for each test. For example, you might use `beforeEach` to create a mock object or to open a database connection.
Use `beforeAll` to set up any state that you need for all tests in a suite. For example, you might use `beforeAll` to create a global variable or to start a server.

Here are some code examples that show how to use the `beforeEach` and `beforeAll` methods:

js
// beforeEach
beforeEach(() => // Set up state that you need for each test
>),

// beforeAll
beforeAll(() => // Set up state that you need for all tests
>),

// Test code
test(‘my test’, () => // Use the state that you set up in beforeEach and beforeAll
>),

The `beforeEach` and `beforeAll` methods are two of the most important test lifecycle methods in Jest. By understanding when to use each one, you can write more efficient and effective tests.

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Meaning of many a true word is spoken in jest in English

That may be a fair picture—many a true word is spoken in jest—but it is certainly not our idea of a heaven upon earth.