cypress-ld-control VS cypress-crud-api-test

I wrote a blog post about it “ Control LaunchDarkly From Cypress Tests” https://glebbahmutov.com/blog/cypress-and-launchdarkly/

My friend Gleb Bahmutov authored an excellent blog on testing LD with Cypress, there he revealed his new plugin cypress-ld-control. We used it in Effective Test Strategies for Front-end Applications using LaunchDarkly Feature Flags and Cypress. Part2: testing. The distinction here is using the plugin for a deployed service and the consequential test strategies.

The cypress-ld-control plugin utilizes cy.task, which allows node code to execute within Cypress context. Therefore we will not be able to use cypress.env.json to store these LD related environment variables locally.

Any blog post is lackluster without working code, so here is a PR from scratch adding esbuild to a repository with Cypress. You can find the final code on the main branch of the repository we will use in this example. Other examples can be found at tour-of-heroes-react-cypress-ts as well as a VueJS app. The framework and the bundler the framework uses are irrelevant, any repo can take advantage of cypress-esbuild-preprocessor for e2e tests.

This is part two of a multi-part series. In the previous post we setup the flags, now we will test them. Before diving into testing feature flags, we will setup Cypress and transfer over the final CRUD e2e spec from the repo cypress-crud-api-test. That repo was featured in the blog post CRUD API testing a deployed service with Cypress. Note that the said repo and this service used to be separated - that is a known anti-pattern - and now we are combining the two in a whole. The change will provide us with the ability to use the LaunchDarkly (LD) client instance to make flag value assertions. We would not have that capability if the test code was in a separate repo than the source code, unless the common code was moved to a package & was imported to the two repos. In the real world if we had to apply that as a solution, we would want to have valuable trade-offs.

The code for this entire guide is available at GitHub. For learning purposes, you can check out the branch base to start from scratch and follow the guide. main has the final version of the repo. The code samples are setup to copy paste into the repo and work at every step.