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cucumber-example-ts-node-react

An example of fullstack typescript testing

Getting Started

Prerequisites

  • node 16, highly recommend nvm for installing and managing versions of node
  • npm 8 (should come with node)

NPM 8 or greater is required because this example uses monorepo workspaces. This can also be achieved with Yarn.

  • Install dependencies for all workspaces (./packages/*) using npm
npm i

Running Cucumber

cd packages/bdd
npm run cucumber -- features/ # add any other cucumber CLI args here

How does it work?

Taking inspiration from https://github.com/subsecondtdd/assembly-diagrams#readme

This is an implementation of a 'DOM-Domain' test assembly. Our BDD Cucumber tests run very fast, in the same nodejs (cucucmber-js) process, exercising both frontend and backend code.

  • Actor
    • Gherkin (.feature)
    • cucumber-js
  • DOM interactions
  • DOM
    • jsdom emulation, under the hood of @testing-library/react
  • React App
  • Domain Session
    • Mocked API calls using msw
  • Domain Logic
    • Emoji Search api example using Fastify

Tips

Test State

In this example you can see use of state attached to the World.

When('I search for {string}', async function(this: World, searchQuery: string) {
  this.state.searchQuery = searchQuery;
  this.emojiSearch.changeSearchInput(searchQuery);
})

Then('I should only see emoji which match the keyword', async function(this: World) {
  this.emojiSearch.assertEmojiListIsNotEmpty();
  this.emojiSearch.assertAllEmojiMatch(this.state.searchQuery as string);
})

Avoid using state as much as possible as it can leak between steps unintentionally and can make testing more difficult than it needs to be.

Assertions

  • expect can be imported separately from Jest and used in Cucumber
    • testing-library/jest-dom can also be used... see here
  • chai also has BDD-style assertions

Profiles to enable/disable api interaction

You can use profiles and world parameters to select frontend-only testing with mocked API responses.

Gotchas

  • React cannot work with more than one instance of itself

Use of yarn or npm workspaces ensures that a single instance of React is installed. Otherwise, importing a React App from frontend will provide an instance of React which conflicts with the instance installed in the bdd test codebase. This will emerge as errors such as this one

  • Create React App, Jest etc. do magic with Webpack

Without the magic of popular development tools, your React app code that imports stuff like .css, .svg, will throw errors while running in cucumber-js. See cucumber.setup.js for one solution.

  • Tests slow to start if typechecking is on

When cucumber-js is running through ts-node, turn off typechecking. See tsconfig.json. If you want this switched on, you can enable it in your IDE or add it to eslint.