jest-fail-on-console

What is jest-fail-on-console?

The jest-fail-on-console npm package is designed to make your Jest tests fail if any console methods (like console.log, console.error, etc.) are called during the test run. This helps ensure that your tests are clean and free of unexpected console output, which can be indicative of underlying issues or forgotten debug statements.

What are jest-fail-on-console's main functionalities?

Fail on console.log

This feature makes the test fail if console.log is called during the test execution. It helps in identifying and removing unnecessary or forgotten console.log statements.

require('jest-fail-on-console');

// In your test file
it('should fail if console.log is called', () => {
  console.log('This will cause the test to fail');
  expect(true).toBe(true);
});

Fail on console.error

This feature makes the test fail if console.error is called during the test execution. It helps in catching errors that are logged to the console, ensuring they are properly handled.

require('jest-fail-on-console');

// In your test file
it('should fail if console.error is called', () => {
  console.error('This will cause the test to fail');
  expect(true).toBe(true);
});

Fail on console.warn

This feature makes the test fail if console.warn is called during the test execution. It helps in identifying and addressing warnings that are logged to the console.

require('jest-fail-on-console');

// In your test file
it('should fail if console.warn is called', () => {
  console.warn('This will cause the test to fail');
  expect(true).toBe(true);
});

Other packages similar to jest-fail-on-console

jest-console

jest-console is a package that provides utilities for testing console output in Jest. Unlike jest-fail-on-console, which fails tests on any console method call, jest-console allows you to assert specific console outputs, giving you more control over what is considered a test failure.

jest-mock-console

jest-mock-console is a package that allows you to mock console methods in your Jest tests. This package is useful for testing how your code handles console output without necessarily failing the test. It provides more flexibility compared to jest-fail-on-console, which strictly fails tests on console method calls.

README

jest-fail-on-console

Utility to make jest tests fail when console.error(), console.warn(), etc. are used

What problem is this solving?

Jest doesn't fail the tests when there is a console.error. In large codebase, we can end up with the test output overloaded by a lot of errors, warnings, etc.. To prevent this, we want to fail each test that is logging to the console. We also want to conserve a clear output of the original error.

This is what this utility is doing.

Downloads

Install

yarn add -D jest-fail-on-console

or

npm install -D jest-fail-on-console

How to use

In a file used in the setupFilesAfterEnv option of Jest, add this code:

import failOnConsole from 'jest-fail-on-console'

failOnConsole()

// or with options:
failOnConsole({
  shouldFailOnWarn: false,
})

But I have some expected console errors/warning

If a console.error() is expected, then you should assert for it:

test('should log an error', () => {
  jest.spyOn(console, 'error').mockImplementation()
  // do your logic
  expect(console.error).toHaveBeenCalledWith('your error message')
})

Options

You can pass an object with options to the function:

errorMessage

Use this if you want to override the default error message of this library.

// signature
type errorMessage = (
  methodName: 'assert' | 'debug' | 'error' | 'info' | 'log' | 'warn',
  bold: (string: string) => string
) => string

shouldFailOnAssert

Use this to make a test fail when a console.assert() is logged.

• Type: boolean
• Default: false

shouldFailOnDebug

Use this to make a test fail when a console.debug() is logged.

• Type: boolean
• Default: false

shouldFailOnError

Use this to make a test fail when a console.error() is logged.

• Type: boolean
• Default: true

shouldFailOnInfo

Use this to make a test fail when a console.info() is logged.

• Type: boolean
• Default: false

shouldFailOnLog

Use this to make a test fail when a console.log() is logged.

• Type: boolean
• Default: false

shouldFailOnWarn

Use this to make a test fail when a console.warn() is logged.

• Type: boolean
• Default: true

allowMessage

// signature
type allowMessage = (
  message: string,
  methodName: 'assert' | 'debug' | 'error' | 'info' | 'log' | 'warn',
  context: { group: string; groups: string[] }
) => boolean

This function is called for every console method supported by this utility. If true is returned, the message will show in the console and the test won't fail.

Example:

failOnConsole({
  allowMessage: (errorMessage) => {
    if (/An expected error/.test(errorMessage)) {
      return true
    }
    return false
  },
})

silenceMessage

// signature
type silenceMessage = (
  message: string,
  methodName: 'assert' | 'debug' | 'error' | 'info' | 'log' | 'warn',
  context: { group: string; groups: string[] }
) => boolean

This function is called for every console method supported by this utility. If true is returned, the message will not show in the console and the test won't fail.

Example:

failOnConsole({
  silenceMessage: (errorMessage) => {
    if (/Not implemented: navigation/.test(errorMessage)) {
      return true
    }
    return false
  },
})

skipTest

Use this if you want to ignore checks introduced by this library for specific tests determined by the return of the callback function. Return false if you do not want to skip console checks for the specific test and return true if you would like to skip it.

const ignoreList = [/.*components\/SomeComponent.test.tsx/]
const ignoreNameList = ['some component some test name']

failOnConsole({
  skipTest: ({ testPath, testName }) => {
    for (const pathExp of ignoreList) {
      const result = pathExp.test(testPath)
      if (result) return true
    }

    if (ignoreNameList.includes(testName)) {
      return true
    }

    return false
  },
})

shouldPrintMessage

Use this to print the message immediately when called not awaiting the test to finish. This is useful to show the message if there are other or earlier test failures which will result in the fail on console error to be hidden by jest.

• Type: boolean
• Default: false

License

MIT

Maintainers

This project is maintained by Valentin Hervieu.

This project was originally part of @ricardo-ch organisation because I (Valentin) was working at Ricardo. After leaving this company, they gracefully accepted to transfer the project to me. ❤️

Credits

Most of the logic is taken from React's setupTests file.