fix: add a test and correct the collateral check (#2300)

packages/zoe/src/contracts/loan/borrow.js

@@ -5,7 +5,7 @@ import { assert, details } from '@agoric/assert';
 import { E } from '@agoric/eventual-send';
 import { makePromiseKit } from '@agoric/promise-kit';
 
-import { assertProposalShape, trade, natSafeMath } from '../../contractSupport';
+import { assertProposalShape, trade } from '../../contractSupport';
 
 import { scheduleLiquidation } from './scheduleLiquidation';
 import { calculateInterest, makeDebtCalculator } from './updateDebt';
@@ -55,9 +55,7 @@ export const makeBorrowInvitation = (zcf, config) => {
     // Assert the required collateral was escrowed.
     assert(
       loanMath.isGTE(
-        loanMath.make(
-          natSafeMath.multiply(collateralPriceInLoanBrand.value, 100),
-        ),
+        loanMath.make(collateralPriceInLoanBrand.value),
         mmr.scale(loanWanted),
       ),
       details`The required margin is approximately ${approxForMsg.value}% but collateral only had value of ${collateralPriceInLoanBrand.value}`,

packages/zoe/test/unitTests/contracts/loan/test-borrow.js

@@ -346,6 +346,19 @@ test('getDebtNotifier with interest', async t => {
   });
 });
 
+test('borrow collateral just too low', async t => {
+  const { borrowSeat: borrowSeatGood } = await setupBorrowFacet(75);
+  const offerResult = await E(borrowSeatGood).getOfferResult();
+  const collateralAmount = await E(offerResult).getRecentCollateralAmount();
+  t.is(collateralAmount.value, 75);
+
+  const { borrowSeat: borrowSeatBad } = await setupBorrowFacet(74);
+  await t.throwsAsync(() => E(borrowSeatBad).getOfferResult(), {
+    message:
+      'The required margin is approximately (a number)% but collateral only had value of (a number)',
+  });
+});
+
 test.todo('borrow bad proposal');
 
 test.todo('schedule a liquidation that fails, giving collateral to the lender');