Auditing and Debugging Vault Implementations — Forge College

Can your tokenized vault survive adversarial inputs and avoid silent accounting drift? Final verification and reproducible debugging are essential before adding permit-based approvals or integrations. What you'll learn In this lesson you will identify and fix logic bugs that commonly afflict tokenized vaults (ERC-4626-style) running on Solana. You'll inspect errors such as off-by-one share math, fee rounding edge cases, and stale account-state assumptions; then write invariant-based unit tests and property tests that codify conservation of assets, monotonic supply rules, and correct fee accrual without balance leakage. The lesson covers practical fuzzing and property-based testing workflows (proptest, cargo-fuzz), tracing cross-account deposit/withdraw flows, and hardening deterministic rounding strategies. You will produce a reproducible debug_report.md and updated tests that fail before fixes and pass after. Who this is for This is an intermediate lesson for Rust/Anchor developers building tokenized vaults on Solana who already know basic account models, Anchor testing, and ERC-style share semantics. Key topics covered - Common vault logic bugs: off-by-one share math, rounding drift, incorrect ownership checks - Invariant and property-based tests asserting conservation of underlying tokens and monotonic supply - Fuzzing and adversarial input strategies using proptest and cargo-fuzz - Debugging cross-account flows: deposit/withdraw atomicity and idempotence - Practical test harness setup: solana-test-validator, Anchor test runner, and targeted test instrumentation - Producing a concise debug report with reproduction steps, fixes, and updated tests Follow the hands-on setup to run a local validator and iterate tests (solana-test-validator --reset && sleep 2; anchor test -- --nocapture). Build the debug_report.md and updated tests in tests/ and programs/vault/src/lib.rs to demonstrate fixes. Start debugging now and harden your vault with reproducible tests: https://www.forge.college/