chore: add provider context mock (#29201)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

web/testing/testing.md

@@ -146,6 +146,8 @@ Treat component state as part of the public behavior: confirm the initial render
 - ✅ Reset shared stores (React context, Zustand, TanStack Query cache) between tests to avoid leaking state. Prefer helper factory functions over module-level singletons in specs.
 - ✅ For hooks that read from context, use `renderHook` with a custom wrapper that supplies required providers.
 
+If it's need to mock some common context provider used across many components (for example, `ProviderContext`), put it in __mocks__/context(for example, `__mocks__/context/provider-context`). To dynamically control the mock behavior (for example, toggling plan type), use module-level variables to track state and change them(for example, `context/provier-context-mock.spec.tsx`).
+
 ### 4. Performance Optimization
 
 Cover memoized callbacks or values only when they influence observable behavior—memoized children, subscription updates, expensive computations. Trigger realistic re-renders and assert the outcomes (avoided rerenders, reused results) instead of inspecting hook internals.