testing

# Dart & Flutter Testing Testing fundamentals for Dart and Flutter projects — unit tests, widget tests, and golden file tests — using `package:test`, `package:flutter_test`, `package:mocktail`, and `package:bloc_test`. ## Core Standards Apply these standards to ALL test work: - **Descriptive test names** — verbose, readable names that describe the behavior; never `'works'` or `'renders'` - **Hierarchical group/test structure that reads as natural sentences** — top-level `group` for the class, nested `group` for the method, `test` for the behavior (e.g., `UserRepository` → `getUser` → `returns User when API succeeds`) - **String interpolation for type references** — use `'returns $User'` not `'returns User'` so renames propagate automatically - **Private mocks per file** — declare `class _MockX extends Mock implements X {}` with underscore prefix to prevent cross-file coupling - **Contained test setup within groups** — all `setUp`/`tearDown` calls live inside a `group`, never at the top level of `main()` - **Initialize mutable objects in `setUp()` with `late`** — declare `late MyDep dep;` then assign in `setUp` so each test gets a fresh instance - **No shared mutable state between tests** — never use static members, global variables, or top-level final instances that persist across tests - **Use `package:mocktail`** — never `package:mockito` - **Constant test tags** — use an `abstract class TestTag` with `static const` fields; never pass raw string literals as tags - **Tes...