feat: implement browser-only test mode (Phase 2)

[goosewobbler]

Mirror Tauri's browser mode for Electron: adds mode='browser' +
devServerUrl to ElectronServiceOptions/GlobalOptions, skips binary
detection and CDP bridge in launcher, injects ipcRenderer IPC stub
into the browser page, and exposes browser.electron.mock(channel) for
test-side IPC channel mocking.

Also extracts WDIO_MOCK_SETUP_SCRIPT from TauriAdapter into a shared
injection.ts constant so both adapters compose from the same browser-
side mock factory, and fully implements ElectronAdapter (previously all
stubs) with all FrameworkAdapter methods.

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com

[github-actions]

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[greptile-apps]

Greptile Summary

This PR implements browser-only test mode for the Electron service (Phase 2), mirroring the existing Tauri browser mode: it adds mode='browser' + devServerUrl config options, skips binary detection and the CDP bridge, injects an ipcRenderer stub into the page, and exposes browser.electron.mock(channel) for IPC mocking. It also extracts the shared browser-side mock factory (WDIO_MOCK_SETUP_SCRIPT) from TauriAdapter into injection.ts, fully implements ElectronAdapter (all methods were previously stubs), and introduces a per-instance MockUpdateScheduler to serialize batched mock-update calls.

• Browser mode plumbing: launcher.ts validates all Electron capabilities share the same mode, strips the Electron binary from goog:chromeOptions, sets browserName: 'chrome', then exits early. service.ts navigates to devServerUrl, injects the IPC stub, patches browser.url() for re-injection on navigation, and exposes the electron.* API surface.
• Shared mock factory: WDIO_MOCK_SETUP_SCRIPT is extracted from TauriAdapter with several bug fixes — mockResolvedValue/mockRejectedValue now record the resolved/rejected value directly (not the Promise object), mockClear uses in-place array mutation (.length = 0) so external references to mock.calls stay valid, and error objects are serialised/reconstructed across the WebDriver boundary.
• Tauri additions: emitEvent is added to TauriServiceAPI for both browser and native modes, and patchBrowserUrl now rethrows on injection failure instead of silently swallowing it.

Confidence Score: 4/5

The browser-mode feature is substantial and well-structured; the most impactful issues from the previous review cycle are addressed. The remaining open concern (installCommandOverrides firing in native mode) is acknowledged and deferred to #268.

The PR adds a large new execution path with complex multiremote and per-instance lifecycle management. The previous review cycle surfaced many issues — mode detection limited to the first cap, devServerUrl validation per-cap, mockResolvedValue serializing a Promise, mockClear replacing arrays, root-browser URL patching, stale mock re-registration, and injection-error swallowing — and this iteration demonstrates careful, targeted fixes for each one. The installCommandOverrides-in-native-mode regression is the only remaining known defect on the changed path, and the developer has explicitly deferred it to a follow-up PR.

packages/electron-service/src/service.ts contains the most complex logic (MockUpdateScheduler, multiremote URL patching, mock store key scheme, concurrent registration gate) and warrants careful review. packages/native-spy/src/interceptor/injection.ts is the shared browser-side mock factory and any bug there affects both Electron and Tauri browser modes.

Important Files Changed

Filename	Overview
packages/electron-service/src/service.ts	Core browser-mode orchestration: initBrowserMode, patchBrowserUrl, getElectronBrowserModeAPI, MockUpdateScheduler, per-instance store keys. Several previously-flagged issues are resolved; residual complexity around multiremote mock ownership remains.
packages/electron-service/src/mock.ts	createElectronBrowserModeMock: all async mock methods, implState tracking for __replayBrowserImpl, full update() sync via IPC interceptor scripts.
packages/electron-service/src/launcher.ts	Validates uniform mode across all capabilities, validates devServerUrl per-cap, strips Electron binary from chromeOptions, skips CDP/binary setup in browser mode. Previously-flagged first-cap-only issues are fixed.
packages/native-spy/src/interceptor/injection.ts	Extracts WDIO_MOCK_SETUP_SCRIPT from TauriAdapter with bug fixes: __wdioType sentinels for resolved/rejected values, in-place array mutation in mockClear, stable _mockSnapshot reference.
packages/native-spy/src/interceptor/electron.ts	Full ElectronAdapter implementation: buildBrowserIpcInjectionScript injects ipcRenderer stub with invoke/send/sendSync + no-op on/once/removeListener/removeAllListeners, all other FrameworkAdapter methods implemented.
packages/native-spy/src/interceptor/tauri.ts	Migrated to shared WDIO_MOCK_SETUP_SCRIPT; adds event subsystem (wdio_tauri_listeners, wdio_emit_tauri_event, wdio_handle_plugin_event) to support browser-mode emitEvent. Error serialization added to buildCallDataReadScript.
packages/tauri-service/src/service.ts	Adds emitEvent to TauriServiceAPI with both browser-mode (via wdio_emit_tauri_event) and native-mode paths; patchBrowserUrl now rethrows on injection failure.
packages/native-spy/src/interceptor/syncProtocol.ts	parseCallData now recursively reconstructs Error objects from __wdioError sentinel, matching the new error serialization in buildCallDataReadScript.
packages/native-spy/src/mock.ts	mockClear changed from array replacement to in-place mutation (.length = 0) to keep external array references valid after vitest-side clear operations.
packages/electron-service/src/mockStore.ts	Adds setMockWithKey (bypasses getMockName key derivation) and deleteMockByRef (reference-equality lookup) for browser-mode instance-scoped keys.
packages/native-types/src/electron.ts	Adds mode and devServerUrl fields to ElectronServiceOptions and ElectronServiceGlobalOptions.
packages/native-types/src/tauri.ts	Adds TauriEventTarget union type mirroring @tauri-apps/api/event; adds emitEvent to TauriServiceAPI.

Sequence Diagram

sequenceDiagram
    participant Test as Test Runner
    participant Launcher as ElectronLaunchService
    participant Service as ElectronWorkerService
    participant Browser as Chrome (browser mode)
    participant Page as App Page

    Test->>Launcher: onPrepare(caps)
    Launcher->>Launcher: "validate all caps same mode='browser'"
    Launcher->>Launcher: validate devServerUrl per-cap
    Launcher->>Launcher: "set browserName='chrome', strip binary"
    Launcher-->>Test: return (skip CDP/binary setup)

    Test->>Service: beforeSession(caps, instance)
    Service->>Service: initBrowserMode(browser)
    Service->>Browser: browser.url(devServerUrl)
    Browser->>Page: navigate
    Service->>Browser: browser.execute(injectionScript)
    Note over Browser,Page: window.__wdio_spy__, window.__wdio_mocks__,<br/>window.electron.ipcRenderer stub injected
    Service->>Browser: patchBrowserUrl() — wraps url() for re-injection
    Service->>Browser: installCommandOverrides() — click/setValue triggers mock sync
    Service->>Browser: "browser.electron = getElectronBrowserModeAPI()"

    Test->>Browser: browser.electron.mock('channel')
    Browser->>Page: execute(buildRegistrationScript)
    Note over Page: window.__wdio_mocks__['channel'] = spy.fn()
    Browser-->>Test: ElectronFunctionMock

    Test->>Browser: browser.url('new-page')
    Browser->>Page: navigate (wipes window)
    Browser->>Page: execute(injectionScript) [re-inject]
    Note over Browser: liveness check in mock() detects !isLive
    Test->>Browser: browser.electron.mock('channel') [re-register]
    Browser->>Page: execute(buildRegistrationScript)
    Browser->>Page: __replayBrowserImpl() [restore impl]
    Browser->>Browser: existing.mockClear()

    Test->>Browser: browser.$('btn').click()
    Browser->>Browser: MockUpdateScheduler.schedule()
    Browser->>Page: execute(buildCallDataReadScript)
    Page-->>Browser: "{ calls, results, invocationCallOrder }"
    Browser->>Browser: mock.update() — sync to Node.js side

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_{Reviews (39): Last reviewed commit: "docs(browser-mode): clarify multiremote ..." | Re-trigger Greptile}