Add VS Code extension test harness for Playwright Local Browser Server

[Copilot]

Implements VS Code extension host testing for command activation validation, per PR #5424 discussion.

Changes

• Test Infrastructure

  • src/test/runTest.ts - @vscode/test-electron runner
  • src/test/suite/index.ts - Mocha suite configuration
  • src/test/suite/extension.test.ts - Extension activation and command registration tests

• Test Coverage

  • Extension activation
  • Command registration for all 6 contributed commands
  • Non-interactive command execution (showLog, showSettings)
  • Package.json consistency validation

• Dependencies

  • Added @vscode/test-electron, mocha, glob with type definitions
  • Added test and pretest npm scripts

Limitations

Interactive commands (start, stop, manageAllowlist, showMenu) are validated for registration only. Execution testing requires mocking UI interactions to avoid blocking on dialogs.

Example

test('Command playwright-local-browser-server.showLog should execute without error', async () => {
  await vscode.commands.executeCommand('playwright-local-browser-server.showLog');
  assert.ok(true, 'showLog command executed');
});

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• update.code.visualstudio.com
  • Triggering command: /usr/local/bin/node node ./lib/test/runTest.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add Test Harness for VS Code Extensions</issue_title>
<issue_description>these command activations can also be tested through the vscode extension host test harness.
https://code.visualstudio.com/api/working-with-extensions/testing-extension

Originally posted by @bmiddha in #5424 (comment)
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add Test Harness for VS Code Extensions #5558

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[TheLarkInn]

We shouldn't be using mocha, what does the rest of the repository use for testing? Follow that pattern.

[Copilot]

We shouldn't be using mocha, what does the rest of the repository use for testing? Follow that pattern.

The existing rush-vscode-extension also uses Mocha for its tests. VS Code extension testing requires running tests inside VS Code's extension host using @vscode/test-electron, which has traditionally used Mocha (as documented in the official VS Code extension testing guide).

However, the rest of the repository uses Jest with Heft's test phase. Would you like me to:

1. Keep Mocha (matching the existing rush-vscode-extension pattern)
2. Switch to Jest with a custom integration for VS Code extension host testing
3. Use Heft's Jest plugin but skip the VS Code extension host integration (limiting what we can test)

Could you clarify which approach you'd prefer?