Add a VestingWallet (#2748)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

test/finance/VestingWallet.test.js

@@ -0,0 +1,67 @@
+const { constants, expectEvent, expectRevert, time } = require('@openzeppelin/test-helpers');
+const { web3 } = require('@openzeppelin/test-helpers/src/setup');
+const { expect } = require('chai');
+
+const ERC20Mock = artifacts.require('ERC20Mock');
+const VestingWallet = artifacts.require('VestingWallet');
+
+const { shouldBehaveLikeVesting } = require('./VestingWallet.behavior');
+
+const min = (...args) => args.slice(1).reduce((x, y) => x.lt(y) ? x : y, args[0]);
+
+contract('VestingWallet', function (accounts) {
+  const [ sender, beneficiary ] = accounts;
+
+  const amount = web3.utils.toBN(web3.utils.toWei('100'));
+  const duration = web3.utils.toBN(4 * 365 * 86400); // 4 years
+
+  beforeEach(async function () {
+    this.start = (await time.latest()).addn(3600); // in 1 hour
+    this.mock = await VestingWallet.new(beneficiary, this.start, duration);
+  });
+
+  it('rejects zero address for beneficiary', async function () {
+    await expectRevert(
+      VestingWallet.new(constants.ZERO_ADDRESS, this.start, duration),
+      'VestingWallet: beneficiary is zero address',
+    );
+  });
+
+  it('check vesting contract', async function () {
+    expect(await this.mock.beneficiary()).to.be.equal(beneficiary);
+    expect(await this.mock.start()).to.be.bignumber.equal(this.start);
+    expect(await this.mock.duration()).to.be.bignumber.equal(duration);
+  });
+
+  describe('vesting schedule', function () {
+    beforeEach(async function () {
+      this.schedule = Array(64).fill().map((_, i) => web3.utils.toBN(i).mul(duration).divn(60).add(this.start));
+      this.vestingFn = timestamp => min(amount, amount.mul(timestamp.sub(this.start)).div(duration));
+    });
+
+    describe('Eth vesting', function () {
+      beforeEach(async function () {
+        await web3.eth.sendTransaction({ from: sender, to: this.mock.address, value: amount });
+        this.getBalance = account => web3.eth.getBalance(account).then(web3.utils.toBN);
+        this.checkRelease = () => {};
+      });
+
+      shouldBehaveLikeVesting(beneficiary);
+    });
+
+    describe('ERC20 vesting', function () {
+      beforeEach(async function () {
+        this.token = await ERC20Mock.new('Name', 'Symbol', this.mock.address, amount);
+        this.getBalance = (account) => this.token.balanceOf(account);
+        this.checkRelease = (receipt, to, value) => expectEvent.inTransaction(
+          receipt.tx,
+          this.token,
+          'Transfer',
+          { from: this.mock.address, to, value },
+        );
+      });
+
+      shouldBehaveLikeVesting(beneficiary);
+    });
+  });
+});