While not foolproof, this approach gives you some confidence, and giving up CPU cycles for mental energy is a pretty good trade. The PSA on writing reliable web tests. also has good guidelines for writing reliable tests. Tests should be self-describing , so that a project member can recognize whether a test passes or fails without having to read the specification of the feature being tested.

js makes a test self-describing when used correctly. Other types of tests, such as reference tests and tests with manual fallback , must be carefully designed to be self-describing.

Avoid depending on edge case behavior of features that aren't explicitly covered by the test. For example, except where testing parsing, tests should contain valid markup no parsing errors.

Tests should provide as much relevant information as possible when failing. Tests should be as cross-platform as reasonably possible.

Avoid assumptions about device type, screen resolution, etc. Unavoidable assumptions should be documented. When possible, tests should only use Web platform features, as specified in the relevant standards.

Tests should avoid using features that haven't been shipped by the actively-developed major rendering engines Blink, WebKit, Gecko, Edge. When unsure, check caniuse. By necessity, this recommendation does not apply to the feature targeted by the test. ES is shipped by all major browsers under active development except for modules , so using ES features is acceptable.

See below for using multiple origins in a test. File names should use snake-case , but preserve the case of any embedded API names. For example, prefer document-createElement. html to document-create-element. This guideline does not apply when specifically testing encodings.

No coding style is enforced for web tests. This section highlights coding style aspects that are not consistent across our web tests, and suggests some defaults for unopinionated developers. When writing web tests for a new part of the codebase, you can minimize review latency by taking a look at existing tests, and pay particular attention to these issues.

Cypress generates its own isolated profile apart from your normal browser profile. This means things like history entries, cookies , and 3rd party extensions from your regular browsing session will not affect your tests in Cypress.

That's no problem - you have to reinstall them once in the Cypress launched browser. We'll continue to use this Cypress testing profile on subsequent launches so all of your configuration will be preserved. Any extra tabs i. tabs other than the one opened by Cypress will be closed between tests. We recommend using your own browser instead of the one launched by Cypress for general-purpose browsing.

Cypress automatically disables certain functionality in the Cypress launched browser that tend to get in the way of automated testing. You can see all of the default chrome command line switches we send here. You might notice that if you already have the browser open you will see two of the same browser icons in your dock.

We understand that when Cypress is running in its own profile it can be difficult to tell the difference between your normal browser and Cypress. For this reason you may find downloading and using a browser's release channel versions Dev, Canary, etc useful. These browsers have different icons from the standard stable browser, making them more distinguishable.

You can also use the bundled Electron browser , which does not have a dock icon. Additionally, in Chrome-based browsers, we've made the browser spawned by Cypress look different than regular sessions. You'll see a darker theme around the chrome of the browser.

You'll always be able to visually distinguish these. Having issues launching installed browsers? Read more about troubleshooting browser launching. Skip to main content. Guides API Plugins Examples FAQ Learn. Cypress GitHub repository Cypress Discord. On this page. When you run tests in Cypress, we launch a browser for you.

This enables us to: Create a clean, pristine testing environment. Access the privileged browser APIs for automation. Cross Browser Support Cypress currently supports Firefox and Chrome-family browsers including Edge and Electron.

cypress run --headed. cypress run --browser chrome. Google Chrome and Microsoft Edge respect enterprise policies, which include limitations to the capabilities, network proxy, mandatory extensions that stand in the way of testing. So if you are part of the organization that uses such policies, it is easiest to use bundled Chromium for your local testing, you can still opt into stable channels on the bots that are typically free of such restrictions.

Playwright's Firefox version matches the recent Firefox Stable build. Playwright doesn't work with the branded version of Firefox since it relies on patches. Playwright's WebKit version matches the recent WebKit trunk build, before it is used in Apple Safari and other WebKit-based browsers.

This gives a lot of lead time to react on the potential browser update issues. Playwright doesn't work with the branded version of Safari since it relies on patches. Instead you can test against the recent WebKit build.

Sometimes companies maintain an internal proxy that blocks direct access to the public resources. In this case, Playwright can be configured to download browsers via a proxy server.

Sometimes companies maintain an internal artifact repository to host browser binaries. You can override default behavior using environment variables.

When installing Playwright, ask it to download browsers into a specific location:. Playwright keeps track of packages that need those browsers and will garbage collect them as you update Playwright to the newer versions.

Playwright keeps track of the clients that use its browsers. When there are no more clients that require a particular version of the browser, that version is deleted from the system. That way you can safely use Playwright instances of different versions and at the same time, you don't waste disk space for the browsers that are no longer in use.

This will remove the browsers chromium, firefox, webkit of the current Playwright installation:. Skip to main content. js Node. js Python Java. Guides Browsers On this page.