Apple QA Engineer System Design Questions

At Apple, maintaining quality code with accurate test results is crucial. Flaky tests can undermine developer confidence and impede productivity. A robust detector for flaky tests can significantly reduce these issues.
Problem statement: Design a component that can analyze the test history and detect tests that have inconsistent results across multiple runs. This component needs the following functionalities:
- logTestResult(testName: str, isSuccess: bool): Logs the outcome of a test run.
- detectFlakyTests() -> List[str]: Identifies and returns a list of flaky tests.
- getTestHistory(testName: str): Retrieves the historical results for a specific test.Example 1:
Input: logTestResult("TestLogin", True)
Output: None
Explanation: The result of TestLogin is logged as successful.Constraints:
- 1 <= testName.length <= 50
- Successful logs must occur in a test history of at least 5 runs.

Apple Music's scalability is vital to ensure a smooth user experience, especially during peak usage. A reliable load testing system can help identify performance bottlenecks before they impact users.
Problem statement: Design and implement a load testing orchestration system for Apple Music that can simulate multiple users interacting with the service. The essential functionalities include:
- startLoadTest(testConfig: LoadTestConfig): Begins the load test with a specific configuration.
- getTestResults() -> LoadTestResults: Returns aggregated results after the test execution.
- stopLoadTest(): Stops the ongoing load test.Example 1:
Input: startLoadTest(LoadTestConfig(100, "peak hours"))
Output: LoadTestResults instance with performance metrics
Explanation: The orchestration system executes a load test simulating 100 users during peak hours and returns the results.Constraints:
- 1 <= userCount <= 1000
- Test configurations must include various metrics such as response time and throughput.