[PR #38] p3: _validParams() sets minSwapOut=0 — slippage floor and swap-output-below-repayment guard untested

[obchain]

Summary

The helper _validParams() sets minSwapOut: 0. This means every test that uses _validParams() accepts a zero slippage floor. The two swap-output protection mechanisms in executeOperation are:

1. amountOutMinimum: p.minSwapOut — passed to PancakeSwap router; reverts if output is below floor
2. require(finalBal >= totalOwed, "swap output below repayment") — defensive check

Neither mechanism is exercised by any test in this PR. There is no test that:

• Sets a non-zero minSwapOut and verifies the revert path when the router returns below that floor
• Verifies the "swap output below repayment" guard fires when post-swap balance is insufficient

Location

contracts/test/CharonLiquidator.t.sol — _validParams() internal helper

Risk

Sandwich attacks and oracle manipulation attacks against the swap step are the primary MEV vectors for this liquidation bot. The slippage floor is the on-chain defense. An unexercised slippage guard may be misconfigured (floor set by the Rust bot to 0 or near-0) without any test surfacing the problem.

Fix

Add two tests (can be mocked):

1. Stub router that returns minSwapOut - 1 tokens; assert revert from router.
2. Stub router that returns enough to partially cover but not meet totalOwed; assert "swap output below repayment" revert.

Refs #38

[obchain]

Fixed via commit 6447016 with two tests:

• test_executeOperation_revertsWhenRouterOutputBelowMinSwapOut sets minSwapOut = 1.5e18 and configures the mock router to return 0.5e18 with enforceMinOut = true; the router reverts with "Too little received" exactly like PancakeSwap V3 does, and the revert bubbles up through executeOperation.
• test_executeOperation_revertsWhenOutputBelowTotalOwed proves the contract's own defensive require(finalBal >= totalOwed, "swap output below repayment") guard fires independently of the router when minSwapOut = 0 and the swap returns less than amount + premium.
  Together these cover both the router-side slippage floor and the contract-side backstop.