add unit test for ChiDiscount (#2170)

Author: kongliangzhong

packages/loopring_v3/contracts/test/Chi/DummyWriteContract.sol

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2017 Loopring Technology Limited.
+pragma solidity ^0.7.0;
+pragma experimental ABIEncoderV2;
+
+import "../../aux/gas/ChiDiscount.sol";
+
+contract DummyWriteContract is ChiDiscount {
+    mapping (address => uint) data;
+    address public chiToken;
+
+    constructor(address _chiToken) {
+        chiToken = _chiToken;
+    }
+
+    function write(ChiConfig calldata config, uint offset)
+        external
+        discountCHI(chiToken, config)
+    {
+        for (uint i = 0; i < 20; i++) {
+            data[address(i + offset)] = i + offset;
+        }
+    }
+}

packages/loopring_v3/test/testChiDiscount.ts

@@ -0,0 +1,102 @@
+import { expectThrow } from "./expectThrow";
+
+const ChiToken = artifacts.require("ChiToken");
+const DummyWriteContract = artifacts.require("DummyWriteContract");
+
+contract("ChiDiscount", (accounts: string[]) => {
+  const owner1 = accounts[0];
+  const owner2 = accounts[1];
+  const owner3 = accounts[2];
+  const emptyAddr = "0x0000000000000000000000000000000000000000";
+
+  let chiToken: any;
+  let dummyWriteContract: any;
+
+  beforeEach(async () => {
+    chiToken = await ChiToken.new();
+    dummyWriteContract = await DummyWriteContract.new(chiToken.address);
+  });
+
+  describe("ChiDiscount", () => {
+    it("should be able to refund gas", async () => {
+      // mint chiToken:
+      const tx0 = await chiToken.mint(100, { gas: 6700000 });
+      const gasAmount0 = tx0.receipt.gasUsed;
+      console.log("mint 100 chiToken, gasUsed:", gasAmount0);
+
+      const balance1 = await chiToken.balanceOf(accounts[0]);
+      assert.equal(100, balance1.toNumber(), "unexpected balance");
+
+      let offset = 0;
+      // write without chiToken burning:
+      const tx1 = await dummyWriteContract.write(
+        {
+          gasTokenVault: "0x" + "00".repeat(20),
+          maxToBurn: 100,
+          expectedGasRefund: 0,
+          calldataCost: 0
+        },
+        offset
+      );
+      console.log("gas used without chiToken:", tx1.receipt.gasUsed);
+
+      offset += 100;
+      // transfer chiToken to writeContract:
+      await chiToken.transfer(dummyWriteContract.address, 100);
+      // write with chiToken burning:
+      const tx2 = await dummyWriteContract.write(
+        {
+          gasTokenVault: "0x" + "00".repeat(20),
+          maxToBurn: 100,
+          expectedGasRefund: 0,
+          calldataCost: 0
+        },
+        offset
+      );
+      console.log("gas used with chiToken:", tx2.receipt.gasUsed);
+      const chiTokenBalanceAfter = await chiToken.balanceOf(
+        dummyWriteContract.address
+      );
+      const chiTokenUsed = 100 - chiTokenBalanceAfter.toNumber();
+      console.log(
+        "chiTokenUsed:",
+        chiTokenUsed,
+        " minted gas amount:",
+        (gasAmount0 * chiTokenUsed) / 100
+      );
+      console.log("gas saved:", tx1.receipt.gasUsed - tx2.receipt.gasUsed);
+
+      offset += 100;
+      // freeFrom test:
+      await chiToken.mint(100, { gas: 6700000 });
+      await chiToken.approve(dummyWriteContract.address, 1000);
+      const chiTokenBalanceBefore3 = (await chiToken.balanceOf(
+        accounts[0]
+      )).toNumber();
+      const tx3 = await dummyWriteContract.write(
+        {
+          gasTokenVault: accounts[0],
+          maxToBurn: 100,
+          expectedGasRefund: 0,
+          calldataCost: 0
+        },
+        offset
+      );
+      console.log("--- freeFrom test ---");
+      console.log("gas used with chiToken (freeFrom):", tx3.receipt.gasUsed);
+      const chiTokenBalanceAfter3 = (await chiToken.balanceOf(
+        accounts[0]
+      )).toNumber();
+      const chiTokenUsed3 = chiTokenBalanceBefore3 - chiTokenBalanceAfter3;
+      console.log(
+        "chiTokenUsed:",
+        chiTokenUsed3,
+        " minted gas amount:",
+        (gasAmount0 * chiTokenUsed3) / 100
+      );
+      console.log("gas saved:", tx1.receipt.gasUsed - tx3.receipt.gasUsed);
+
+      assert(true);
+    });
+  });
+});