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Add test_borrow_apy #91

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Nov 23, 2022
Merged

Add test_borrow_apy #91

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0394bab
Add test_borrow_apy
rockyfour Nov 22, 2022
f89e368
hevm => vm
rockyfour Nov 23, 2022
ca926c4
Make comment about Compound UI a bit clearer
rockyfour Nov 23, 2022
155b9bf
Add back a test that was falsely removed
rockyfour Nov 23, 2022
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3 changes: 2 additions & 1 deletion src/plans/D3MCompoundPlan.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,8 @@
// apy to rate per block off-chain conversion info:
// apy = ((1 + (borrowRatePerBlock / WAD) * blocksPerDay) ^ 365 - 1) * 100
// (0) borrowRatePerBlock = ((((apy / 100) + 1) ^ (1 / 365) - 1) / blocksPerDay) * WAD
// ATTOW the formula matches the borrow apy on (https://compound.finance/markets/DAI) using blocksPerDay = 6570
// Initially the formula matched the borrow apy on (https://compound.finance/markets/DAI) using blocksPerDay = 6570
// blocksPerDay was later updated to 7200.
//
// https://github.com/compound-finance/compound-protocol/blob/a3214f67b73310d547e00fc578e8355911c9d376/contracts/BaseJumpRateModelV2.sol#L96
//
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38 changes: 23 additions & 15 deletions src/tests/integration/D3MCompound.t.sol
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Expand Up @@ -45,6 +45,8 @@ interface CErc20Like {
function balanceOfUnderlying(address owner) external returns (uint256);
function repayBorrow(uint256 repayAmount) external returns (uint256);
function exchangeRateCurrent() external returns (uint256);
function accrueInterest() external returns (uint256);
function borrowBalanceCurrent(address) external returns (uint256);
}

interface CEthLike {
Expand All @@ -69,6 +71,9 @@ interface InterestRateModelLike {
}

contract D3MCompoundTest is DSSTest {
Hevm hevm;
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bytes20 constant CHEAT_CODE = bytes20(uint160(uint256(keccak256('hevm cheat code'))));

VatLike vat;
EndLike end;
CErc20Like cDai;
Expand Down Expand Up @@ -97,6 +102,7 @@ contract D3MCompoundTest is DSSTest {
emit log_named_uint("block", block.number);
emit log_named_uint("timestamp", block.timestamp);

hevm = Hevm(address(CHEAT_CODE));
vat = VatLike(0x35D1b3F3D7966A1DFe207aa4514C12a259A0492B);
end = EndLike(0x0e2e8F1D1326A4B9633D96222Ce399c708B19c28);
cDai = CErc20Like(0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643);
Expand Down Expand Up @@ -300,26 +306,28 @@ contract D3MCompoundTest is DSSTest {
assertEq(vat.dai(address(d3mHub)), 0);
}

function test_target_increase() public {
// Lower by 50%
uint256 targetBorrowRate = _setRelBorrowTarget(5000);
function test_borrow_apy() public {
// target 2% borrow apy, see top of D3MCompoundPlan for the formula explanation
uint256 targetBorrowRate = 7535450719; // ((2.00 / 100) + 1) ^ (1 / 365) - 1) / 7200) * 10^18

d3mCompoundPlan.file("barb", targetBorrowRate);
d3mHub.exec(ilk);
assertEqInterest(getBorrowRate(), targetBorrowRate);

uint256 amountSuppliedInitial = cDai.balanceOfUnderlying(address(d3mCompoundPool));
cDai.borrow(1 * WAD);

// Raise by 25%
targetBorrowRate = _setRelBorrowTarget(12500);
assertEqInterest(getBorrowRate(), targetBorrowRate);
uint256 borrowBalanceBefore = cDai.borrowBalanceCurrent(address(this));

uint256 amountSupplied = cDai.balanceOfUnderlying(address(d3mCompoundPool));
assertTrue(amountSupplied > 0);
assertLt(amountSupplied, amountSuppliedInitial);
(uint256 ink, uint256 art) = vat.urns(ilk, address(d3mCompoundPool));
assertEqRounding(ink, amountSupplied);
assertEqRounding(art, amountSupplied);
// fast forward 1 year while accruing interest each day
for (uint256 i = 1; i <= 365; i++) {
hevm.roll(block.number + 7200);
cDai.accrueInterest();
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}

assertEq(vat.gem(ilk, address(d3mCompoundPool)), 0);
assertEq(vat.dai(address(d3mHub)), 0);
uint256 borrowBalanceAfter = cDai.borrowBalanceCurrent(address(this));

// rates compound so we tolerate a larger difference
assertEqApprox(borrowBalanceAfter, borrowBalanceBefore * 102 / 100, INTEREST_RATE_TOLERANCE * 5);
}

function test_barb_zero() public {
Expand Down