Danger JS Testing

About this project

This project was created to allow a developer to test their DangerJS dangerfile through Jest unit testing. It also works with testing imported DangerJS plugins.

Getting started

:warning: This project is currently going through ramp up development.
Some things may change, some things may not work. Submit issues if you find any.

This package requires a minimum Danger and Jest version to function but it may function with future and previous versions as well. Create an issue/discussion if you test a version outside the required versions that you have found that works.

Installation

Until published install via direct GitHub link

$ npm install danger-testing --save-dev

This project assumes that Danger and Jest are already installed in your project.

Usage

Move dangerfile checks into a function or separate functions if you haven't done so previously.

// dangerfileFunctions.ts

// break your checks into functions that are exported.
// 📢 optionally, put all the functions inside a bigger function 
// that's exported to test closer to how Danger would report.
export const checkLineAdditions = () => {
  if (danger.github.pr.additions > 500) {
    warn('PR exceeds number of lines added')
  }
}

Create a test file like dangerfile.spec.ts to write your tests.

// dangerfile.spec.ts
import { dangerTesting, warn } from 'danger-js-testing'
import { checkLineAdditions } from '../dangerfile'

it('should call warn function if PR additions exceed 500 lines of code', async() => {
  await dangerTesting(checkLineAdditions, {
    github: {
      pr: {
        additions: 900,
      },
    },
  })

  expect(warn).toHaveBeenCalledWith(
    'PR exceeds number of lines added'
  )
  expect(warn).toHaveBeenCalledTimes(1)
})

How it works

Takes inspiration from the documentation on the Danger website and myself wanting to have an easy way to test Danger during development.

The dangerTesting function accepts two arguments. One is the dangerfile function you have written for your tests. The second is the mock override we attach to the global danger object.

When dangerTesting is called it updates the global mock and then calls the passed in function.

This module exports danger like global mock functions like fail, markdown, message, and warn, to allow you to check that they are called as expected.