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How to Clear the Cache in Jest in JavaScript

Jest maintains a cache of transformed module files to make running tests faster. However, this cache can sometimes become stale or corrupted after upgrading dependencies, changing configurations (like Babel or TypeScript), or when tests behave unexpectedly. Clearing the Jest cache is a common and effective troubleshooting step.

This guide will teach you the standard command-line method for clearing the cache, how to add a convenient npm script for it, and how to disable the cache for debugging purposes.

The Core Method (Recommended): jest --clearCache​

The simplest and most direct way to clear the cache is by using the --clearCache command-line flag. This command will delete the entire Jest cache directory and then exit without running any tests.

The solution is to open your terminal in your project's root directory and run the following command.

npx jest --clearCache
note

Why npx? Using npx ensures that you are running the version of jest that is installed locally in your project's node_modules, which is the recommended best practice. If you have jest installed globally, you can run jest --clearCache directly.

After the command completes, you can run your tests as usual, and Jest will create a fresh cache.

Adding a package.json Script for Convenience​

To avoid having to remember the --clearCache flag, you can add a dedicated script to your package.json file.

The solution is to open your package.json file and add a clear-cache script.

{
  "scripts": {
    "test": "jest",
    "clear-cache": "jest --clearCache"
  }
}

Now, you can simply run the following command to clear the cache:

# Using npm
npm run clear-cache

# Using yarn
yarn clear-cache

How to Disable the Cache for a Single Run​

If you are debugging an issue that you suspect is related to caching, you can temporarily disable the cache for a single test run using the --no-cache flag.

warning

Warning: Running tests without the cache will be significantly slower (often more than twice as slow). This should only be used for temporary debugging.

Solution:

npx jest --no-cache

You can also add this to your test script in package.json if needed, but it's not recommended for permanent use due to the performance impact.

// In package.json (for temporary debugging only)
"scripts": {
  "test": "jest --no-cache"
}

A Note on jest.resetModules()​

It's important not to confuse clearing the global Jest cache with resetting the module cache within a test suite. The jest.resetModules() helper function is used inside a test file (often in a beforeEach block) to ensure that modules are re-imported and do not share state between tests.

// This resets the module cache for each test in this file.
// It does NOT clear the global Jest file transform cache.
beforeEach(() => {
  jest.resetModules();
});

Conclusion​

Clearing the Jest cache is a simple but powerful troubleshooting step for resolving unexpected test failures and configuration issues.

  • The recommended best practice is to run npx jest --clearCache from your terminal.
  • Adding a clear-cache script to your package.json is a convenient way to make this command easily accessible.
  • Use the --no-cache flag only for temporary debugging, as it has a significant performance penalty.

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