[good first issue] Add EIP-2612 permit() fuzz tests for Stablecoin

[abhicris]

Context

contracts/Stablecoin.sol includes EIP-2612 permit() support for gasless approvals. forge-test/Stablecoin.t.sol does not fuzz permit signatures — we only have a happy-path check (if any). Permit is a high-risk surface (signature-malleability, expired deadlines, replay via nonce reuse) and deserves property-based coverage.

Scope

Files to touch:

• forge-test/Stablecoin.t.sol — add a new test contract or section PermitTests.
• Use vm.sign + vm.warp to fuzz (owner, spender, value, deadline, nonce) tuples.

Cases to cover:

• Valid permit lifts allowance and increments nonce.
• Expired deadline reverts.
• Wrong-chain / wrong-verifyingContract reverts.
• Signature replay (same nonce twice) reverts.

Acceptance criteria

• 4+ new fuzz tests, each with explicit assertEq / vm.expectRevert.
• forge test passes locally.

Estimated effort

M — 3 hrs.

— kcolbchain / Abhishek Krishna

[ilainy]

I'd like to work on this. Please assign it to me.

[MyTH-zyxeon]

Opened PR #43 with EIP-2612 permit fuzz coverage: #43

It covers valid permits, expired deadlines, wrong-chain domains, wrong verifying contracts, and replay with nonce reuse. Local validation: FOUNDRY_LIBS=["node_modules","/tmp/codex-forge-libs"] FOUNDRY_TEST=forge-test forge test --match-contract StablecoinTest -vv -> 22 passed; fmt and diff checks passed.