Systematic Regression Test Expansion for ESP

This project focuses on systematically expanding regression test coverage for the ESP codebase by targeting high-risk, untested logic paths rather than merely increasing overall coverage percentage. Through detailed codebase exploration, critical gaps have been identified in components such as lottery assignment logic, class registration flows, and mailman integrations. These areas involve complex logic, invariants, and edge cases that currently lack sufficient test coverage and pose a high risk of silent regressions. The project introduces invariant-based testing for the lottery system to ensure correctness properties such as no conflicts, no overcapacity, and valid grade constraints across arbitrary inputs. Additionally, integration tests will be implemented for mailman functionality using mocking to validate subprocess interactions without external dependencies. A reusable testing infrastructure will be developed to support scalable regression testing, along with targeted performance checks to detect potential degradations in critical views. The outcome will be a robust regression testing framework that transforms fragile, untested paths into enforceable guarantees, significantly improving system reliability and maintainability.