Three tests in tests/background/onboarding.test.ts pinning the
Plan 01-10 D-17-onboarding contract:
Test A (RED): first install + empty storage opens exactly ONE welcome
tab whose URL contains 'src/welcome/welcome.html', sets
chrome.storage.local.set({'onboarding-completed':true,
'installed-at':<number>}), AND calls chrome.storage.local.get with
EXACT key 'onboarding-completed' (storage-schema cross-version-compat
pin; preserves I-02 lesson from prior draft).
Test B (vacuous-GREEN, becomes load-bearing post-Task-3): reason='update'
→ chrome.tabs.create NOT called.
Test C (vacuous-GREEN, becomes load-bearing post-Task-3): flag already
true → chrome.tabs.create NOT called.
Tests B and C pass vacuously until Task 3 lands openWelcomeIfFirstInstall;
they remain load-bearing AFTER Task 3 as no-tab-open guards for the
update/already-onboarded branches. Test A flips RED → GREEN at Task 3.
Stub scaffold inherits buildBgStub from onstartup-notification.test.ts;
extended with chrome.tabs.create + chrome.storage.local.{get,set} +
chrome.runtime.onInstalled._callbacks (addListener.mockImplementation
pattern to capture the SW's registered listener).
DEVIATION NOTE: plan's <verify> expected `3 failed` but only Test A
(positive contract) goes RED pre-Task-3; Tests B+C are negative-path
guards that pass trivially when the helper is absent. This is standard
TDD (positive test fails RED; negative tests stay GREEN through GREEN→
REFACTOR). No code change needed — Task 3's GREEN gate is "all 3 GREEN".
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
