Error: "React-Jest error: node:internal/process/promises:288 triggerUncaughtException(err, true /* fromPromise */); TypeError"


This error often occurs when running Jest tests for a React application, and it is related to unhandled promise rejections. It is important to address the underlying cause to prevent this error from disrupting your test suite.

Solution:

  1. Update Jest: Ensure you are using the latest version of Jest, as newer versions often include bug fixes and improvements. Update your project's dependencies to the latest Jest version by running:

    Example: 

              npm install --save-dev jest

  2. Check Asynchronous Code: Review your test suite for asynchronous code (promises, async/await) and make sure you are handling errors properly. Ensure that every promise is either awaited or properly chained with `.then()` and `.catch()`.

    Example: 

              test('Example Async Test', async () => {
            // Async code that returns a promise
            await expect(asyncFunction()).resolves.toBe('expectedValue');
          });

  3. Update Node.js: Ensure you are using a version of Node.js that is compatible with your Jest version. Upgrade Node.js to the latest LTS version if needed.

  4. Check Global Jest Configuration: Review your Jest configuration in your `package.json` or `jest.config.js` file. Ensure that it is correctly set up and does not conflict with any other configurations.

    Example: 

              @*package.json*@
          "jest": {
            "testEnvironment": "jsdom"
          }

After applying these solutions, run your Jest tests again. If the issue persists, carefully review your test code for any unhandled promise rejections or asynchronous code that might be causing the error.

Error: "NodeJS with ESM: internal/process/promises:246 | triggerUncaughtException(err, true /* fromPromise */) | finalizer.unsubscribe is not a function"

This error occurs when using Node.js with ECMAScript Modules (ESM), and it is related to an issue with the handling of promises. It typically points to a problem with promise handling or finalization in your code.

Solution:

  1. Update Node.js: Ensure you are using a version of Node.js that supports ESM and includes the necessary improvements and bug fixes. Upgrade Node.js to the latest LTS version if needed.

  2. Check Import Statements: When using ESM, ensure that your import statements use the `import` syntax. Verify that you are not mixing CommonJS (`require`) and ESM syntax in the same file.

    Example: 

              // ESM syntax
          import fs from 'fs';
          import { someFunction } from './myModule.js';

  3. Check Promise Handling: Review your code for promise handling and ensure that you are using the correct methods, such as `async/await` or `.then()` and `.catch()`. Verify that promises are properly handled and finalized.

    Example: 

              async function exampleAsyncFunction() {
            try {
              const result = await someAsyncOperation();
              console.log(result);
            } catch (error) {
              console.error('Error:', error);
            }
          }

  4. Update Dependencies: Ensure that your project dependencies, especially those related to ESM and promise handling, are up to date. Check for updates and make necessary changes to package versions.

  5. Review Third-Party Modules: If you are using third-party modules, check their documentation and GitHub issues for compatibility with ESM and Node.js versions. Update or switch to alternative modules if needed.

After applying above solutions, run your Node.js application again. If the issue persists, review your code for any specific areas where promises are used and ensure they are handled correctly.

Error: "Jest on promises: triggerUncaughtException(err, true /* fromPromise */)"


This error occurs in Jest when a Promise rejection is not handled properly within your test suite. Jest is detecting an unhandled Promise rejection and is signaling an issue with your asynchronous code or lack of error handling.

Solution:

  1. Check Test Code: Review your Jest test code for asynchronous operations using Promises, async/await, or callback functions. Ensure that you are handling errors appropriately and that every Promise is either awaited or chained with `.then()` and `.catch()`.

    Example: 

              test('Example Async Test', async () => {
            // Async code that returns a promise
            await expect(asyncFunction()).resolves.toBe('expectedValue');
          });

  2. Use Jest Helpers: Leverage Jest helpers like `resolves`, `rejects`, and `expect.assertions()` to assert the expected behavior of your asynchronous code. This helps Jest to properly handle Promise rejections.

    Example: 

              test('Example Async Test with expects', () => {
            expect.assertions(1);
            return expect(asyncFunction()).resolves.toBe('expectedValue');
          });

  3. Update Jest: Ensure you are using the latest version of Jest, as newer versions often include improvements and bug fixes. Update your project's dependencies to the latest Jest version by running:

    Example: 

              npm install --save-dev jest

  4. Check Node.js Version: Ensure that you are using a version of Node.js that is compatible with your Jest version. Upgrade Node.js to the latest LTS version if needed.

  5. Review Global Jest Configuration: Check your Jest configuration in your `package.json` or `jest.config.js` file. Ensure that it is correctly set up and does not conflict with any other configurations.

    Example: 

              // package.json
          "jest": {
            "testEnvironment": "jsdom"
          }

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