Improve AMM tests
We strongly recommend creating a more thorough testing suite for dex.move, stableswap.move, and minitswap.move to ensure correctness. Subtle bugs hiding in code are less likely to exist when the test suite is comprehensive. Ensure the test suite is comprehensive — covering edge cases and extreme values — and achieves as close to 100% code coverage as possible. Additionally, consider implementing fuzz testing and formal verification where applicable using the Move prover.