Write UI Tests

Background: Native [iOS / Android] app, [SwiftUI / Compose]. The flow I
want to test end to end: [describe—e.g., log in, add an item, see it in
the list]. 

Use case: Write UI/integration tests that drive the real screens and
verify the user-visible behavior.

Implementation details:
- iOS: XCUITest, or SwiftUI/ViewInspector-style view tests for lighter
  cases; use accessibility identifiers for stable element queries.
  Android: Compose UI test (createComposeRule) for composables, Espresso
  for full-flow; use test tags / semantics for stable matchers.
- Stub the network/backend so tests are deterministic (launch in a test
  mode with fakes), not hitting production
- Cover the happy path plus one key failure (e.g., login error shown)
- Handle async waiting via the framework's idling/awaiting, not sleeps
- Keep these few and high-value (they're slow)

Layer & dependencies: Inject fakes at app launch for test builds so the
UI runs against controlled data.

Deliverable: The UI test(s) for the flow, the stable element-matching
strategy (identifiers/tags), the launch/fake-injection setup for
determinism, and guidance on which flows are worth UI-testing vs not.