cypress-ld-control

Set LaunchDarkly feature flags from Cypress tests

Read the blog post Control LaunchDarkly From Cypress Tests.

Install

Add this plugin as a dev dependency

# install using NPM
$ npm i -D cypress-ld-control
# install using Yarn
$ yarn add -D cypress-ld-control

Most common use case: using this plugin from Cypress

Add the plugin to your Node-side plugins or config file

// cypress.config.js
// https://github.com/bahmutov/cypress-ld-control
const { initCypress } = require('cypress-ld-control')
...
e2e: {
  setupNodeEvents(on, config) {
    initCypress(on, config)
    // IMPORTANT: return the updated config object
    return config
  },
}

If you want custom cy commands to fetch or control the feature flags, include the plugin's commands file from your support file or from your spec file:

// your support or spec file
// https://github.com/bahmutov/cypress-ld-control
import 'cypress-ld-control/commands'

API

Commands

From the spec or browser support file you can import the cypress-ld-control/commands module to add utility commands

isLaunchDarklyControlInitialized

Static, chained off Cypress

if (Cypress.isLaunchDarklyControlInitialized()) {
  // we can control the LaunchDarkly flags
}

getFeatureFlag

cy.getFeatureFlag(featureFlagKey).then(flag => ...)

setFeatureFlagForUser

cy.setFeatureFlagForUser(featureFlagKey, userId, variationIndex)

removeUserTarget

cy.removeUserTarget(featureFlagKey, userId)

Plugin Node API

This plugin provides the following functions

getFeatureFlags

Returns all feature flags. Warning: could be a lot of flags!

const flags = await ldApi.getFeatureFlags()
// flags is an array of objects

getFeatureFlag

Returns a large object with everything there is two know about the feature flag in a particular environment

const flag = ldApi.getFeatureFlag('my-feature-flag')

setFeatureFlagForUser

Important: the feature flag must have "Targeting: on" for user-level targeting to work.

await ldApi.setFeatureFlagForUser({
  featureFlagKey: 'my-flag-key',
  userId: 'string user id',
  variationIndex: 1, // must be index to one of the variations
})

removeTarget

Removes the specified target object

await ldApi.removeTarget({
  featureFlagKey: 'my-flag-key',
  targetIndex: 0,
})

removeUserTarget

Removes the given user from any variation targeting lists for the given feature

await ldApi.removeUserTarget({
  featureFlagKey: 'my-flag-key',
  userId: 'user string id',
})

Use without Cypress

You can use this plugin by itself to control LaunchDarkly flags

// https://github.com/bahmutov/cypress-ld-control
const { initLaunchDarklyApiClient } = require('cypress-ld-control')
const ldApi = initLaunchDarklyApiClient({
  projectKey: process.env.LAUNCH_DARKLY_PROJECT_KEY,
  authToken: process.env.LAUNCH_DARKLY_AUTH_TOKEN,
  environment: 'test', // the key of the environment to use
})
const flag = await ldApi.getFeatureFlag('my-flag-key')
await ldApi.setFeatureFlagForUser({
  featureFlagKey: 'my-flag-key',
  userId: '1234567',
  variationIndex: 0, // index of the variant to use
})

See demo/index.js

Use from Cypress

Add the plugin to your Cypress plugins file by grabbing an object with tasks.

initCypress

From your Cypress config file (v10+) or from your plugins file, call the initCypress function.

// cypress.config.js
const { initCypress } = require('cypress-ld-control')
setupNodeEvents(on, config) {
  initCypress(on, config)
  // IMPORTANT: return the updated config object
  return config
}

Reads the environment variables LAUNCH_DARKLY_PROJECT_KEY and LAUNCH_DARKLY_AUTH_TOKEN to initialize the LD client. You can pass the LD environment name via LAUNCH_DARKLY_ENVIRONMENT, otherwise it assumes the LD environment name is "test".

initCypressMultipleProjects

Sometimes you might have several LaunchDarkly projects. You can control each one, and all you need is LAUNCH_DARKLY_AUTH_TOKEN environment variable.

// cypress.config.js
const { initCypressMultipleProjects } = require('cypress-ld-control')
setupNodeEvents(on, config) {
  // list all the LD projects you want to use
  const projects = [
    {
      projectKey: 'demo-project',
      environment: 'test',
    },
    {
      projectKey: 'api-project',
      environment: 'test',
    },
  ]

  initCypressMultipleProjects(projects, on, config)

  // IMPORTANT: return the updated config object
  return config
}

When calling the cy custom commands from commands.js pass the project key, for example

cy.getFeatureFlag(featureFlagKey, projectKey)

Project names

Since some projects might have "default" as the project key, you can give them your own "name"

// list all the LD projects you want to use
const projects = [
  {
    name: 'web-flags',
    projectKey: 'default',
    environment: 'test',
  },
  {
    projectKey: 'api-project',
    environment: 'test',
  },
]

initCypressMultipleProjects(projects, on, config)

In the situation above you can get the flag for first project using either of the two keys:

cy.getFeatureFlag('my-flag', 'default')
cy.getFeatureFlag('my-flag', 'web-flags')

Explicit registration (old)

Tip: you might want to check if the environment variables and are set and only initialize the tasks in that case.

// cypress/plugins/index.js
const { initLaunchDarklyApiTasks } = require('cypress-ld-control')
module.exports = (on, config) => {
  const tasks = {
    // add your other Cypress tasks if any
  }

  // https://github.com/bahmutov/cypress-ld-control
  if (
    process.env.LAUNCH_DARKLY_PROJECT_KEY &&
    process.env.LAUNCH_DARKLY_AUTH_TOKEN
  ) {
    const ldApiTasks = initLaunchDarklyApiTasks({
      projectKey: process.env.LAUNCH_DARKLY_PROJECT_KEY,
      authToken: process.env.LAUNCH_DARKLY_AUTH_TOKEN,
      environment: 'test', // the key of the environment to use
    })
    // copy all LaunchDarkly methods as individual tasks
    Object.assign(tasks, ldApiTasks)
  } else {
    console.log('Skipping cypress-ld-control plugin')
  }

  // register all tasks with Cypress
  on('task', tasks)

  // IMPORTANT: return the updated config object
  return config
}

Each method from the API (see above) has a matching task prefixed with cypress-ld-control: string. For example, to see a particular flag from your spec call:

// in your Cypress spec file
// let's find everything about a feature flag
cy.task('cypress-ld-control:getFeatureFlag', 'my-flag-key').then(flag => {...})
// let's set the feature variation for a user
cy.task('cypress-ld-control:setFeatureFlagForUser', {
  featureFlagKey: 'my-flag-key',
  userId: 'string user id',
  variationIndex: 1 // must be index to one of the variations
})

Examples

• application bahmutov/cypress-ld-control-example

Types

In src/index.d.ts file and src/globals.d.ts

Small print

Author: Gleb Bahmutov <[e-mail]> © 2022

• @bahmutov
• glebbahmutov.com
• blog
• videos
• presentations
• cypress.tips
• Cypress Tips & Tricks Newsletter

License: MIT - do anything with the code, but don't blame me if it does not work.

Support: if you find any problems with this module, email / tweet / open issue on Github

MIT License

Copyright (c) 2022 Gleb Bahmutov <[e-mail]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.