test: add simulations for swapping the debt

script/hardhat/fork/vip-99.ts

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+import { SignerWithAddress } from "@nomiclabs/hardhat-ethers/signers";
+import { expect } from "chai";
+import { BigNumber } from "ethers";
+import { parseEther, parseUnits } from "ethers/lib/utils";
+import { ethers } from "hardhat";
+
+import {
+  Comptroller,
+  IERC20Upgradeable,
+  PriceOracle,
+  SwapDebtDelegate,
+  VBep20,
+  VBep20Delegate,
+} from "../../../typechain";
+import { forking, pretendExecutingVip, testVip } from "./vip-framework";
+import { ProposalType } from "./vip-framework/types";
+import { initMainnetUser, makeProposal } from "./vip-framework/utils";
+
+const COMPTROLLER = "0xfd36e2c2a6789db23113685031d7f16329158384";
+const BNB_BRIDGE_EXPLOITER = "0x489A8756C18C0b8B24EC2a2b9FF3D4d447F79BEc";
+const VBUSD = "0x95c78222B3D6e262426483D42CfA53685A67Ab9D";
+const VUSDC = "0xecA88125a5ADbe82614ffC12D0DB554E2e2867C8";
+const VUSDT = "0xfD5840Cd36d94D7229439859C0112a4185BC0255";
+const VETH = "0xf508fCD89b8bd15579dc79A6827cB4686A3592c8";
+const VBTC = "0x882C173bC7Ff3b7786CA16dfeD3DFFfb9Ee7847B";
+const CONFIGURE_ATTACKER_COMPTROLLER_IMPL = "0xAE37464537fDa217258Bb2Cd70e4f8ffC7E95790";
+const NEW_COMPTROLLER_IMPL = "0x909dd16b24CEf96c7be13065a9a0EAF8A126FFa5";
+const NEW_VTOKEN_IMPL = "0x10FB44C481F87cb4F3ce8DE11fFd16e00EC5B670";
+const SWAP_DEBT_DELEGATE = "0x2B16DB59c6f20672C0DB46b80361E9Ca1CD8a43a";
+const BINANCE_MULTISIG = "0x6d46692f809d485A033dA95B19b556E3Ff0ACb12";
+
+const vip99 = () => {
+  const meta = {
+    version: "v2",
+    title: "VIP-99 Delegate borrowing",
+    description: `
+    `,
+    forDescription: "I agree that Venus Protocol should proceed with ",
+    againstDescription: "I do not think that Venus Protocol should proceed with ",
+    abstainDescription: "I am indifferent to whether Venus Protocol proceeds with ",
+  };
+
+  return makeProposal(
+    [
+      {
+        target: COMPTROLLER,
+        signature: "_setPendingImplementation(address)",
+        params: [CONFIGURE_ATTACKER_COMPTROLLER_IMPL],
+      },
+      {
+        target: CONFIGURE_ATTACKER_COMPTROLLER_IMPL,
+        signature: "_become(address)",
+        params: [COMPTROLLER],
+      },
+      {
+        target: COMPTROLLER,
+        signature: "setDelegateForBNBHacker(address)",
+        params: [SWAP_DEBT_DELEGATE],
+      },
+      {
+        target: COMPTROLLER,
+        signature: "_setPendingImplementation(address)",
+        params: [NEW_COMPTROLLER_IMPL],
+      },
+      {
+        target: NEW_COMPTROLLER_IMPL,
+        signature: "_become(address)",
+        params: [COMPTROLLER],
+      },
+      ...[VBUSD, VUSDC, VUSDT, VBTC, VETH].map((vToken: string) => {
+        return {
+          target: vToken,
+          signature: "_setImplementation(address,bool,bytes)",
+          params: [NEW_VTOKEN_IMPL, false, "0x"],
+        };
+      }),
+    ],
+    meta,
+    ProposalType.REGULAR,
+  );
+};
+
+forking(25918391, () => {
+  testVip("VIP-99 Delegate borrowing", vip99(), {
+    proposer: "0xc444949e0054a23c44fc45789738bdf64aed2391",
+    supporter: "0x55A9f5374Af30E3045FB491f1da3C2E8a74d168D",
+  });
+});
+
+// Ressetting the fork to prevent oracle prices from getting stale
+forking(25918391, () => {
+  let comptroller: Comptroller;
+  let busd: IERC20Upgradeable;
+  let usdt: IERC20Upgradeable;
+  let btc: IERC20Upgradeable;
+  let vBUSD: VBep20Delegate;
+  let vUSDC: VBep20Delegate;
+  let vUSDT: VBep20Delegate;
+  let vBTC: VBep20Delegate;
+  let vETH: VBep20Delegate;
+  let swapDebtDelegate: SwapDebtDelegate;
+  let oracle: PriceOracle;
+
+  before(async () => {
+    comptroller = await ethers.getContractAt("Comptroller", COMPTROLLER);
+    [vBUSD, vUSDC, vUSDT, vBTC, vETH] = await Promise.all(
+      [VBUSD, VUSDC, VUSDT, VBTC, VETH].map((address: string) => {
+        return ethers.getContractAt("VBep20Delegate", address);
+      }),
+    );
+    [busd, , usdt, btc] = await Promise.all(
+      [vBUSD, vUSDC, vUSDT, vBTC, vETH].map(async (vToken: VBep20) => {
+        const underlying = await vToken.underlying();
+        return ethers.getContractAt("IERC20Upgradeable", underlying);
+      }),
+    );
+    const oracleAddress = await comptroller.oracle();
+    oracle = await ethers.getContractAt("PriceOracle", oracleAddress);
+    swapDebtDelegate = await ethers.getContractAt("SwapDebtDelegate", SWAP_DEBT_DELEGATE);
+    await pretendExecutingVip(vip99());
+  });
+
+  describe("Post-VIP contracts status", async () => {
+    it("updates vBUSD, vUSDC, vUSDT, vBTC, vETH implementation to the new version", async () => {
+      for (const vToken of [vBUSD, vUSDC, vUSDT, vBTC, vETH]) {
+        expect(await vToken.implementation()).to.equal(NEW_VTOKEN_IMPL);
+      }
+    });
+
+    it("sets Comptroller implementation to the new version", async () => {
+      expect(await comptroller.comptrollerImplementation()).to.equal(NEW_COMPTROLLER_IMPL);
+    });
+
+    it("sets the delegate for BNB bridge exploiter", async () => {
+      expect(await comptroller.approvedDelegates(BNB_BRIDGE_EXPLOITER, SWAP_DEBT_DELEGATE)).to.equal(true);
+    });
+  });
+
+  describe("BNB bridge exploiter debt swap", async () => {
+    let binanceMultisig: SignerWithAddress;
+    let repayAmount: BigNumber;
+
+    before(async () => {
+      binanceMultisig = await initMainnetUser(BINANCE_MULTISIG, parseEther("1"));
+      await swapDebtDelegate.connect(binanceMultisig).acceptOwnership();
+    });
+
+    beforeEach(async () => {
+      const busdHolder = await initMainnetUser(BNB_BRIDGE_EXPLOITER, parseEther("1"));
+      repayAmount = parseUnits("1000000", 18); // one million BUSD
+      await busd.connect(busdHolder).transfer(BINANCE_MULTISIG, repayAmount);
+      await busd.connect(binanceMultisig).approve(swapDebtDelegate.address, repayAmount);
+    });
+
+    it("swaps BUSD debt to USDT debt", async () => {
+      const tx = await swapDebtDelegate
+        .connect(binanceMultisig)
+        .swapDebt(BNB_BRIDGE_EXPLOITER, vBUSD.address, vUSDT.address, repayAmount);
+      const busdPrice = await oracle.getUnderlyingPrice(VBUSD);
+      const usdtPrice = await oracle.getUnderlyingPrice(VUSDT);
+      const borrowedAmount = repayAmount.mul(busdPrice).div(usdtPrice);
+      expect(borrowedAmount).to.equal(parseUnits("999880.752177709989496153", 18));
+      await expect(tx).to.emit(vBUSD, "RepayBorrow").withArgs(
+        SWAP_DEBT_DELEGATE, // payer
+        BNB_BRIDGE_EXPLOITER, // borrower
+        repayAmount,
+        parseUnits("62570837.271361800039742166", 18),
+        parseUnits("118656538.075710219424628656", 18),
+      );
+
+      await expect(tx).to.emit(vUSDT, "Borrow").withArgs(
+        BNB_BRIDGE_EXPLOITER, // borrower
+        borrowedAmount,
+        parseUnits("51791626.908005102781624591", 18), // account's borrows
+        parseUnits("146773356.517479562888182714", 18), // total market borrows
+      );
+
+      expect(await busd.balanceOf(BINANCE_MULTISIG)).to.equal(0);
+      expect(await usdt.balanceOf(BINANCE_MULTISIG)).to.equal(parseUnits("999880.752177709989496153"));
+    });
+
+    it("swaps BUSD debt to BTC debt", async () => {
+      const tx = await swapDebtDelegate
+        .connect(binanceMultisig)
+        .swapDebt(BNB_BRIDGE_EXPLOITER, vBUSD.address, vBTC.address, repayAmount);
+      const busdPrice = await oracle.getUnderlyingPrice(VBUSD);
+      const btcPrice = await oracle.getUnderlyingPrice(VBTC);
+      const borrowedAmount = repayAmount.mul(busdPrice).div(btcPrice);
+      expect(borrowedAmount).to.equal(parseUnits("41.467723055552676044", 18));
+      await expect(tx).to.emit(vBUSD, "RepayBorrow").withArgs(
+        SWAP_DEBT_DELEGATE, // payer
+        BNB_BRIDGE_EXPLOITER, // borrower
+        repayAmount,
+        parseUnits("61570838.645557291459272559", 18), // account's borrows
+        parseUnits("117656540.681673105060252768", 18), // total market borrows
+      );
+
+      await expect(tx).to.emit(vBTC, "Borrow").withArgs(
+        BNB_BRIDGE_EXPLOITER, // borrower
+        borrowedAmount,
+        borrowedAmount, // there were no Bitcoin borrows before
+        parseUnits("2115.100441504922154141", 18), // total market borrows
+      );
+
+      expect(await busd.balanceOf(BINANCE_MULTISIG)).to.equal(0);
+      expect(await btc.balanceOf(BINANCE_MULTISIG)).to.equal(parseUnits("41.467723055552676044"));
+    });
+  });
+});