VS Code extension: real Electron E2E tests via Playwright

[stevez]

Problem

Phase 1 (#526) uses mock-based tests borrowed from playwright-vscode. While fast and CI-friendly, mocks can drift from real VS Code behavior. Real Electron E2E tests would catch integration issues (activation, commands, keybindings, webview rendering).

Approach

Use Playwright's _electron.launch() to launch a real VS Code instance with the extension installed.

Blocker: _electron.launch() broken for Electron 30+

Playwright's _electron.launch() is currently broken for modern VS Code (Electron 30+). The issue:

• Playwright injects --remote-debugging-port=0 as a CLI arg
• Electron 30+ rejects this flag at the CLI level before any JS executes
• A fix was merged (#39012) then reverted (#39710) due to VS Code regressions
• Latest report (#39922, Mar 29 2026) closed as "not planned"
• Microsoft's own playwright-vscode tests-integration also fails on Windows with the same error

Timeline

• #39008 — Original bug report (Jan 2026)
• #39012 — Fix: "pass port via switches not args" (merged Jan 28)
• #39710 — Fix reverted (broke VS Code / Electron 39)
• #39922 — Reopened for Electron 40, closed "not planned" (Mar 29)

Workarounds

1. Use older VS Code (pre-Electron 30, ~VS Code < 1.90) — fragile, outdated
2. Spawn VS Code manually + connect via CDP (wdio approach) — bypass _electron.launch entirely
3. Wait for upstream fix in Playwright

Test infrastructure prepared

Files exist at packages/vscode/e2e/ ready to use once the blocker is resolved:

• globalSetup.ts — downloads VS Code
• playwright.config.ts — test config
• tests/baseTest.ts — fixture that launches VS Code with _electron.launch()
• tests/basic.test.ts — extension activation, Test Explorer, REPL panel tests

References

• Playwright Electron API
• wdio-vscode-service — spawns VS Code + Chromedriver (workaround approach)
• playwright-vscode tests-integration — also affected by this bug
• Feature request: VS Code as Playwright target

Depends on

• VS Code extension: add E2E tests #526 (mock-based tests establish the test scenarios)
• Upstream Playwright fix for _electron.launch() with Electron 30+

[stevez]

Closing — the mock test suite (178 tests, 72% coverage) provides sufficient coverage without Electron overhead. Real Electron E2E is too heavy, flaky, and slow for CI. Can revisit if VS Code ships a lightweight test API.