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End-to-end (E2E) testing

Cypress is used to provide browser-level full-stack testing.

In this project, Cypress gets run within the cypress-workspace holobranch defined at .holo/branch/cypress-workspace/** within the project repository. This allows local test suite additions and overrides to be stacked on top of those provided by parent projects. The base implemenation is published from emergence-skeleton and your local project may have any number of parent projects stacked in between, so there can be many layers contributing to the below content structure.

The cypress-workspace holobranch typically copies the following overrides from the local project repository:

  • cypress.json: top-level project configuration for cypress
  • cypress/integrations/**/*.js: additional or overridden test suites
  • cypress/integrations/**/*.json: additional or overridden test suite configurations (provides some flexibility for test suites to support different downstream reskinnings without all their code needing to be duplicated and overridden)
  • cypress/fixtures/**: static content test suites can make use of

Less commonly, the following files might also be copied from the local project repository to override the Cypress setup in more depth:

  • cypress/support/index.js: Cypress plugins and additional commands get loaded here for all test suites
  • package.json/package-lock.json: Tracks the Cypress version and those of installed plugin packages

Try to avoid having copies of these in local project repositories:

  • cypress/support/commands.js: Base set of additional commands that test suites can rely on. Instead of overridding this file, add additional project-specific commands to some new files under cypress/support and override cypress/support/index.js to load them
  • cypress/plugins/index.js: Base set of automatic environment setup logic

Run tests quickly

To quickly run the full test suite headlessly, run on the local terminal outside the studio in the root of your local project repository:

script/test

Run tests interactively

To run tests with Cypress’ interactive GUI open, run on the local terminal outside the studio in the root of your local project repository:

script/test-interactive

This script uses unionfs-fuse to set up a virtual directory mount on your workstation’s filesystem to run Cypress out of. This union mount provides a live workspace where your local project workspace is merged on top of the base set of cypress-workspace content pulled from your parent project.

This virtual directory mount gets set up at ${path_to_your_repo}.cypress-workspace/merged and Cypress gets run from there.

  • Changes you save to Cypress content in your local project work tree will immediately be reflected in the merged mount
    • The filesystem events needed to drive auto-reload may not work
    • Exit the Cypress GUI and reload it to thoroughly force your latest content to be used
  • Changes you save to Cypress content in your local merged mount will immediately be reflected back to your local project work tree
  • If parent project content changes / you’ve edited a source config, exit the Cypress GUI and re-run script/test-interactive to restart in a fresh environment

Making Cypress auto-reload as you save changes

Because filesystem change events from your local project work tree to the merged unionfs that Cypress runs out of don’t always work, work on Cypress tests out of the merged mount instead.

Any changes you make will immediately be written to to your local project work tree ready to stage into a git commit, and filesystem change events will fire live for Cypress to auto-reload test suites as you work.

The Open in IDE button that Cypress’ main window will how you as you hover over tests in the list can be used to open the copy of the file in the merged mount where changes will trigger auto-reload.

Prevent VSCode from opening virtual repository

By default, Visual Studio Code will automatically detect and open the “merged” git repository produced by the unionfs with its built-in git integration. This makes it difficult to close out the testing environment as VSCode will keep many active processes accessing the git repository once it has been opened, even after you manually close it.

To prevent Visual Studio Code from automatically opening this union repository and causing all sorts of mahem, open your user settings.json and add an option to ignore the *.cypress-workspace/merged repository at whatever path your project repository lives at:

{
    // ...
    "git.ignoredRepositories": [
        "/Users/me/Repositories/git@github.com:SlateFoundation/slate-cbl.git.cypress-workspace/merged"
    ]
}

Testing against a remote server

By setting environment variables before launching the Cypress GUI, the E2E test suite can be configured to execute against a backend studio hosted on a remote machine or server.

On the local terminal outside the studio in the root of your local project repository:

  1. Set base URL to studo HTTP root reachable from local workstation:

    export CYPRESS_BASE_URL='http://workstation.mydomain:2190'

  2. Configure the SSH host that the backend studio is running on:

    export CYPRESS_STUDIO_SSH='workstation.mydomain'

    Your local terminal must be set up to connect to it without password.

  3. Configure the name of the Docker container running the backend studio:

    export CYPRESS_STUDIO_CONTAINER='slate-cbl-studio'

  4. Launch the Cypress GUI:

    script/test-interactive

Checking for race conditions

Cypress’ default timeout limits for UI assertions and XHR assertions vary greatly: 4 seconds for UI assertions and 30 seconds for XHR assertions. This disparity is a leading cause of apparent instability in Cypress tests where a test will pass locally consistently but fail in CI consistency.

What causes this to happen is having UI assertions within your tests that won’t pass if some XHR call leading up to them takes more than 4 seconds, which is more likely to happen occasionally on “cold” instances like CI runs always are. The solution to this is relatively simple: add a cy.wait('@xhrInterceptName') assertion ahead of any UI assertion that won’t pass until that XHR call finishes. This ensures that the test script waits for XHR calls to finish under the longer timeout they have by default, and gives you more helpful errors when a failure happens at that level.

It can be easy to miss these spots while you’re developing tests. One step is to look through your test logs for all XHR calls (they’ll show up in the actions log timeline whether you intercept or wait for them or not) and consider if any of the UI assertions surrounding it depend on it finishing first. Another approach is to introduce an artificial delay to all XHR calls on your local server, forcing them all to take longer than the default UI assertion timeout of 4 seconds:

<?php
// save to php-config/Site.config.d/delay-execute.php

Site::$onBeforeScriptExecute = function() {
    sleep(5);
};

With this change loaded up into your local studio, every request that isn’t a static asset request will gain a 5 second delay upfront—forcing every UI assertion in your test that accidentally depends on an XHR call finishing in less than 4 seconds to fail. Spend one round after you finish your new Cypress tests checking them with this activated, and you can gain a lot of confidence it will work as consistently in CI as it does locally. Just be sure to discard this change when you’re done and avoid committing it with your work—or add it to your local .git/info/exclude to keep it around entirely ignored by Git while you do your work.