Cypress: Functional tests
We are using Cypress for functional testing as much as possible. The key features of Cypress:
- Integration testing with API testing support (Node.js)
- Easy to debug
- Selector playground
- Great documentation
- Best implementation of Live Reloading
Why Cypress is categorised in the pre-deployed tests
The Cypress tests, if structured correctly, can be run BEFORE the app client is deployed to an environment. This is to ensure that we get the fastest feedback we can. If you are following branching strategies such as GitFlow, then you can run these tests on your branch before merging to master.
|deployment independent||not full integration tests as not running on deployed infrastructure|
|run core tests before the branch is merged to master, smoke tests post-merge and deployment|
How Cypress is run in Continuous Integration (CI) pipelines
Glad you asked. You'll see an npm script in the
package.json which uses start-server-and-test. This package starts the Node.js Express server, waits for the app URL (localhost in this case), then runs test command; when the tests end, it shuts down the server instance.
Key benefits means we never have to explicitly wait for the server to be ready before testing.
"test:cypress" : "env CI=true node_modules/.bin/start-server-and-test start $APP_BASE_URL:$PORT test:cypress:run"
How to use Cypress
Please read Cypress - Best Practices for how to get the most out of Cypress.
How to use Cypress while developing
Server Side Rendered (SSR) apps
Say if you are following Test Driven Development (TDD) cycles, or if you wish to write a failing test for a known bug, and fix the app and check to ensure that the test passes, you may wish you watch the tests and the code together.
To open and run Cypress locally with live reload, after installing dependencies:
Install app dependencies
Build the web app
npm run build
*.cy.tsCypress test files
npm run test:cypress:compile
--watchthrough to watch for changes)
Start the server, run the tests headless, tear down the server:
npm run test:cypress
When writing tests: Open Cypress with live-reloading and selector playground.
npm run test:cypress:open
How to run all the tests without keeping the server running
Server Side Rendered (SSR) applications
To spin up the server automatically, then run Cypress in headless Chrome, use:
npm run test:cypress. This is the same script as mentioned for running in CI pipelines
Where tests should be located
We suggest co-locating the
*.cy.ts tests with the page compositions (a composition is several components that may come together to form a page). for high-level tests, and component tests with the components themselves.
│ ├── index.test.cy.ts
│ └── index.tsx
│ └── index.test.tsx.snap
How to configure the environments
We suggest tightly coupling Cypress with the app under test. This means sharing environment configuration files. This ensures that in your deployment pipelines, and quality gating process, you are confident that the app under test is being tested correctly.
For example, if an API URL changes, you will only have a single place to change and the tests and app will be updated together.
Note that the environment variables are required on the hosting platform, e.g.