Add Multicall module (#2608)

test/utils/Multicall.test.js

@@ -0,0 +1,57 @@
+const { BN, expectRevert } = require('@openzeppelin/test-helpers');
+const MulticallTokenMock = artifacts.require('MulticallTokenMock');
+
+contract('MulticallToken', function (accounts) {
+  const [deployer, alice, bob] = accounts;
+  const amount = 12000;
+
+  beforeEach(async function () {
+    this.multicallToken = await MulticallTokenMock.new(new BN(amount), { from: deployer });
+  });
+
+  it('batches function calls', async function () {
+    expect(await this.multicallToken.balanceOf(alice)).to.be.bignumber.equal(new BN('0'));
+    expect(await this.multicallToken.balanceOf(bob)).to.be.bignumber.equal(new BN('0'));
+
+    await this.multicallToken.multicall([
+      this.multicallToken.contract.methods.transfer(alice, amount / 2).encodeABI(),
+      this.multicallToken.contract.methods.transfer(bob, amount / 3).encodeABI(),
+    ], { from: deployer });
+
+    expect(await this.multicallToken.balanceOf(alice)).to.be.bignumber.equal(new BN(amount / 2));
+    expect(await this.multicallToken.balanceOf(bob)).to.be.bignumber.equal(new BN(amount / 3));
+  });
+
+  it('returns an array with the result of each call', async function () {
+    const MulticallTest = artifacts.require('MulticallTest');
+    const multicallTest = await MulticallTest.new({ from: deployer });
+    await this.multicallToken.transfer(multicallTest.address, amount, { from: deployer });
+    expect(await this.multicallToken.balanceOf(multicallTest.address)).to.be.bignumber.equal(new BN(amount));
+
+    const recipients = [alice, bob];
+    const amounts = [amount / 2, amount / 3].map(n => new BN(n));
+
+    await multicallTest.testReturnValues(this.multicallToken.address, recipients, amounts);
+  });
+
+  it('reverts previous calls', async function () {
+    expect(await this.multicallToken.balanceOf(alice)).to.be.bignumber.equal(new BN('0'));
+
+    const call = this.multicallToken.multicall([
+      this.multicallToken.contract.methods.transfer(alice, amount).encodeABI(),
+      this.multicallToken.contract.methods.transfer(bob, amount).encodeABI(),
+    ], { from: deployer });
+
+    await expectRevert(call, 'ERC20: transfer amount exceeds balance');
+    expect(await this.multicallToken.balanceOf(alice)).to.be.bignumber.equal(new BN('0'));
+  });
+
+  it('bubbles up revert reasons', async function () {
+    const call = this.multicallToken.multicall([
+      this.multicallToken.contract.methods.transfer(alice, amount).encodeABI(),
+      this.multicallToken.contract.methods.transfer(bob, amount).encodeABI(),
+    ], { from: deployer });
+
+    await expectRevert(call, 'ERC20: transfer amount exceeds balance');
+  });
+});