openzeppelin-contracts/test/crowdsale/MintedCrowdsale.behaviour.js

const BigNumber = web3.BigNumber;

const should = require('chai')
  .use(require('chai-as-promised'))
  .use(require('chai-bignumber')(BigNumber))
  .should();

export default function ([_, investor, wallet, purchaser], rate, value) {
  const expectedTokenAmount = rate.mul(value);

  describe('as a minted crowdsale', function () {
    describe('accepting payments', function () {
      it('should accept payments', async function () {
        await this.crowdsale.send(value).should.be.fulfilled;
        await this.crowdsale.buyTokens(investor, { value: value, from: purchaser }).should.be.fulfilled;
      });
    });

    describe('high-level purchase', function () {
      it('should log purchase', async function () {
        const { logs } = await this.crowdsale.sendTransaction({ value: value, from: investor });
        const event = logs.find(e => e.event === 'TokenPurchase');
        should.exist(event);
        event.args.purchaser.should.equal(investor);
        event.args.beneficiary.should.equal(investor);
        event.args.value.should.be.bignumber.equal(value);
        event.args.amount.should.be.bignumber.equal(expectedTokenAmount);
      });

      it('should assign tokens to sender', async function () {
        await this.crowdsale.sendTransaction({ value: value, from: investor });
        let balance = await this.token.balanceOf(investor);
        balance.should.be.bignumber.equal(expectedTokenAmount);
      });

      it('should forward funds to wallet', async function () {
        const pre = web3.eth.getBalance(wallet);
        await this.crowdsale.sendTransaction({ value, from: investor });
        const post = web3.eth.getBalance(wallet);
        post.minus(pre).should.be.bignumber.equal(value);
      });
    });
  });
}