jest-fail-on-console

Utility to make jest tests fail when console.error() or console.warn() 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 and warnings. To prevent this, we want to fail each test that is logging an error or a warning to the console. We also want to conserve a clear output of the original error.

This is what this utility is doing.

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:

shouldFailOnWarn

Use this to make a test fail when a warning is logged.

• Type: boolean
• Default: true

shouldFailOnError

Use this to make a test fail when an error is logged.

• Type: boolean
• Default: true

shouldFailOnLog

Use this to make a test fail when a message is logged.

• Type: boolean
• Default: false

silenceMessage

• Signature: (message: string, methodName: 'warn' | 'error') => boolean

This function is called for every console warn/error. 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
  },
})

Credits

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