app-check/REVIEW_GUIDELINES.md

Review Guidelines

Concurrency & Thread Safety

When reviewing Objective-C code, particularly test fakes, you MUST strictly enforce the following thread safety rules for concurrent test execution:

1. State Mutation Synchronization: All state mutations (e.g., incrementing counters like counter++, setting properties, or adding to arrays) MUST be wrapped in a @synchronized(self) block to prevent data races and TSAN (Thread Sanitizer) failures.
2. Proper Use of atomic vs nonatomic: The atomic property modifier does NOT make read-modify-write operations (like ++) thread-safe. Properties that require compound operations should be declared nonatomic to avoid misleading expectations, and their getters/setters must be manually synchronized in the implementation file (or accessed directly via ivar within a synchronized block).