Stripe QA Engineer System Design Questions

To maintain the reliability of our software, identifying tests that intermittently fail is crucial. Stripe needs a system that can intelligently analyze test outcomes to flag flaky tests.
Problem statement: Design a system that collects test run results over time, analyzes patterns, and flags tests with inconsistent results.
- class FlakyTestDetector: The main class for detecting flaky tests.
- def __init__(self) -> None: Initializes the detector with a history of test results.
- def add_run(self, test_id: str, result: bool) -> None: Adds a test run result to the history.
- def find_flaky_tests(self) -> List[str]: Identifies and returns a list of flaky test IDs.
Example 1:
Input: detector = FlakyTestDetector()
Output: None
Explanation: Initializes a Flaky Test Detector.
Example 2:
Input: detector.add_run('test1', True)
Output: None
Explanation: Records the result of a test run.
Constraints:
- 1 <= number of runs <= 10^5

As part of Stripe's commitment to quality, capturing and aggregating test results efficiently is vital to monitor the health of our deployments.
Problem statement: Design a system that collects test results from multiple sources, aggregates them, and provides an interface to access the aggregated data.
- class TestResultAggregator: The main class for managing test results.
- def __init__(self) -> None: Initializes the aggregator.
- def add_result(self, result: TestResult) -> None: Adds a new test result to the aggregator.
- def get_summary(self) -> Summary: Returns an overview of the results collected.
Example 1:
Input: aggregator = TestResultAggregator()
Output: None
Explanation: Initializes a new test result aggregator.
Example 2:
Input: aggregator.add_result(TestResult(1, True))
Output: None
Explanation: Adds the test result to the aggregator.
Constraints:
- 1 <= number of results <= 10^6