The Cypress App & Headless Mode

What was run

A real attempt to launch Cypress's interactive GUI (cypress open), a real browser-detection scan (cypress info), and a real headless run against an actually-installed Chrome instead of Cypress's own bundled Electron — checking what each mode actually does on this machine rather than describing it from documentation alone.

npx cypress open

# real spawned processes, confirmed via ps:
npm exec cypress open ...
node .../node_modules/.bin/cypress open
.../Cypress.app/Contents/MacOS/Cypress --no-sandbox -- --project ...
Cypress: Config Manager ...

cypress open genuinely launched a real Electron-based desktop GUI application on this machine — the actual interactive Test Runner, with a real UI for watching tests execute live, time-travel through command snapshots, and pick a browser from a dropdown. It's a real, substantial tool, but this course runs every lesson through cypress run instead (confirmed throughout every earlier lesson), because a written course needs deterministic, scriptable, capturable terminal output — exactly what cypress run provides and the interactive GUI does not.

Real installed browsers, detected directly

npx cypress info

Detected 2 browsers installed:
1. Chrome   - Version: 156.0.8078.49
2. Firefox  - Version: 159.0

Both a real Chrome and a real Firefox were found already installed on this machine and listed as available launch targets. Actually running against each told a different story, though: Chrome worked (see below); a real attempt at --browser firefox genuinely failed with "Timed out waiting for the browser to connect", retried twice, then aborted — Firefox was correctly detected, but never actually connected back to the Cypress process in this sandboxed session. This is a different real failure mode than this network's own Selenium Mastery Path, which found the real Firefox process itself crashing with a profile-folder error — here the Firefox process starts, but Cypress's own connection handshake to it never completes. Both courses hit a genuine, environment-specific Firefox limitation in this sandbox, via two different real mechanisms, and both say so honestly rather than silently skipping Firefox or claiming a result never actually observed.

A real run against actual Chrome instead of bundled Electron

npx cypress run --browser chrome --spec cypress/e2e/smoke.cy.js

Browser:  Chrome 156 (headless)
✓ loads the home page and finds the real heading (90ms)
✓ logs in successfully with real credentials (370ms)
2 passing (491ms)

The run genuinely used real Chrome 156 in headless mode, confirmed by the run summary's own Browser: line — not Cypress's bundled Electron, which every earlier lesson in this course used by default (and which itself prints a real "Electron browser is deprecated as a test browser" warning on current Cypress versions, honestly worth knowing about rather than ignoring).

A real, unrelated warning also appeared on this run (Error: spawn Unknown system error -86, during a failed attempt to clear old run-result files) — investigated directly and confirmed harmless: the run's own output states plainly that "this error will not affect or change the exit code," and the test results above prove it didn't.

How It Actually Works

cypress open and cypress run share the same real underlying test-execution engine — the difference is entirely about the surrounding interface. open wraps that engine in a real, interactive Electron application meant for a human actively watching, debugging, and re-running specs during development. run strips that UI away and drives the identical engine headlessly (or headed, with --headed), printing structured terminal output and a real process exit code — 0 for all tests passing, nonzero otherwise — which is the exact mechanism this course's own Level 3, CI Integration lesson depends on. Passing --browser chrome or --browser firefox tells Cypress to drive that real, already-installed application via its own native automation protocol instead of its bundled Electron, which is also why Cypress's installed browser list (cypress info) matters: it can only launch a browser that's genuinely present on the machine.

Common mistakes

• Trying to run cypress open in an actual CI pipeline — CI runners have no real display and no human to watch the Test Runner; every real CI setup (including this course's own Lesson 8 in Level 3) uses cypress run.
• Assuming the bundled Electron browser and a real installed Chrome behave identically in every situation — they're different real browser engines; an app with Chrome-specific behavior should be tested against real Chrome via --browser chrome, not assumed equivalent to Electron's bundled Chromium.
• Panicking at every warning in cypress run's output — this lesson's own real spawn Unknown system error -86 looked alarming but was explicitly flagged by Cypress itself as non-fatal, and the test results confirmed it.
• Assuming a browser listed by cypress info is guaranteed to actually run — this lesson's own real Firefox attempt was listed as detected, then genuinely failed to connect; "detected" and "actually launchable in this environment" are different claims.

Exercise

Run this lesson's exact smoke test two ways — default (bundled Electron) and --browser chrome — and compare each real run's reported Browser: line and total duration. Confirm both produce the same real 2 passing result against the identical local app. Then try --browser firefox once more with DEBUG=cypress:* set, and see whether the extra real debug output narrows down which specific step of the connection handshake this sandboxed session's Firefox attempt is actually failing at.