Cypress · Browser testing end to end
What is the Cypress Test Runner and what does it show?
Short answer
The Test Runner is the interactive app opened by cypress open. It lists specs, runs them in a browser, and shows the command log, DOM snapshots, errors and network activity for each step.
The Test Runner is the development-facing half of Cypress. It launches a browser, loads the selected spec, and displays a sidebar of specs plus a command log for the running test. The log is the main debugging surface: each command is a row with a snapshot of the application at that moment.
The runner also lets you choose a browser, rerun a spec, and inspect failed commands. It is not the same as cypress run, which executes specs headlessly and reports results without the interactive UI.
What the log gives you
- Command names, selectors and assertion results
- DOM snapshots for before and after each command
- Error messages with the failing assertion and timeout
- A network view of requests made during the test
- The ability to pin a snapshot and inspect elements in DevTools
npx cypress open
npx cypress open --browser chrome
npx cypress open --componentFollow-ups you should expect
Interviewers use these to check whether the first answer was understanding or memorisation.
- 1What is the difference between cypress open and cypress run?
- 2How do you inspect the DOM at a previous command?
- 3Why can open mode pass while CI fails?
- 4How do you open component tests instead of e2e tests?
Say it in the interview
The Test Runner is the interactive app opened with cypress open. It lists specs, runs them in a browser and shows the command log with DOM snapshots for each step. I use it to author and debug tests, because I can inspect exactly what the page looked like at a failure. For CI I use cypress run, which runs headlessly and reports results without the interactive UI.
Use this as a model, not a script. Saying it in your own words is what makes it survive follow-up pressure.
Related questions
Reading is step one
Now say it out loud.
Understanding an answer and delivering it under pressure are different skills. Rehearse this topic in a live Cypress mock interview and get scored feedback on depth, clarity and confidence.