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ERC20.behavior.js
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ERC20.behavior.js
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const { ethers } = require('hardhat');
const { expect } = require('chai');
function shouldBehaveLikeERC20(initialSupply, opts = {}) {
const { forcedApproval } = opts;
beforeEach(async function () {
[this.holder, this.recipient, this.other] = this.accounts;
});
it('total supply: returns the total token value', async function () {
expect(await this.token.totalSupply()).to.equal(initialSupply);
});
describe('balanceOf', function () {
it('returns zero when the requested account has no tokens', async function () {
expect(await this.token.balanceOf(this.other)).to.equal(0n);
});
it('returns the total token value when the requested account has some tokens', async function () {
expect(await this.token.balanceOf(this.holder)).to.equal(initialSupply);
});
});
describe('transfer', function () {
beforeEach(function () {
this.transfer = (from, to, value) => this.token.connect(from).transfer(to, value);
});
shouldBehaveLikeERC20Transfer(initialSupply);
});
describe('transfer from', function () {
describe('when the token owner is not the zero address', function () {
describe('when the recipient is not the zero address', function () {
describe('when the spender has enough allowance', function () {
beforeEach(async function () {
await this.token.connect(this.holder).approve(this.recipient, initialSupply);
});
describe('when the token owner has enough balance', function () {
const value = initialSupply;
beforeEach(async function () {
this.tx = await this.token.connect(this.recipient).transferFrom(this.holder, this.other, value);
});
it('transfers the requested value', async function () {
await expect(this.tx).to.changeTokenBalances(this.token, [this.holder, this.other], [-value, value]);
});
it('decreases the spender allowance', async function () {
expect(await this.token.allowance(this.holder, this.recipient)).to.equal(0n);
});
it('emits a transfer event', async function () {
await expect(this.tx).to.emit(this.token, 'Transfer').withArgs(this.holder, this.other, value);
});
if (forcedApproval) {
it('emits an approval event', async function () {
await expect(this.tx)
.to.emit(this.token, 'Approval')
.withArgs(
this.holder.address,
this.recipient.address,
await this.token.allowance(this.holder, this.recipient),
);
});
} else {
it('does not emit an approval event', async function () {
await expect(this.tx).to.not.emit(this.token, 'Approval');
});
}
});
it('reverts when the token owner does not have enough balance', async function () {
const value = initialSupply;
await this.token.connect(this.holder).transfer(this.other, 1n);
await expect(this.token.connect(this.recipient).transferFrom(this.holder, this.other, value))
.to.revertedWithCustomError(this.token, 'ERC20InsufficientBalance')
.withArgs(this.holder, value - 1n, value);
});
});
describe('when the spender does not have enough allowance', function () {
const allowance = initialSupply - 1n;
beforeEach(async function () {
await this.token.connect(this.holder).approve(this.recipient, allowance);
});
it('reverts when the token owner has enough balance', async function () {
const value = initialSupply;
await expect(this.token.connect(this.recipient).transferFrom(this.holder, this.other, value))
.to.be.revertedWithCustomError(this.token, 'ERC20InsufficientAllowance')
.withArgs(this.recipient, allowance, value);
});
it('reverts when the token owner does not have enough balance', async function () {
const value = allowance;
await this.token.connect(this.holder).transfer(this.other, 2);
await expect(this.token.connect(this.recipient).transferFrom(this.holder, this.other, value))
.to.be.revertedWithCustomError(this.token, 'ERC20InsufficientBalance')
.withArgs(this.holder, value - 1n, value);
});
});
describe('when the spender has unlimited allowance', function () {
beforeEach(async function () {
await this.token.connect(this.holder).approve(this.recipient, ethers.MaxUint256);
this.tx = await this.token.connect(this.recipient).transferFrom(this.holder, this.other, 1n);
});
it('does not decrease the spender allowance', async function () {
expect(await this.token.allowance(this.holder, this.recipient)).to.equal(ethers.MaxUint256);
});
it('does not emit an approval event', async function () {
await expect(this.tx).to.not.emit(this.token, 'Approval');
});
});
});
it('reverts when the recipient is the zero address', async function () {
const value = initialSupply;
await this.token.connect(this.holder).approve(this.recipient, value);
await expect(this.token.connect(this.recipient).transferFrom(this.holder, ethers.ZeroAddress, value))
.to.be.revertedWithCustomError(this.token, 'ERC20InvalidReceiver')
.withArgs(ethers.ZeroAddress);
});
});
it('reverts when the token owner is the zero address', async function () {
// transferFrom does a spendAllowance before moving the assets
// - default behavior (ERC20) is to always update the approval using `_approve`. This will fail because the
// approver (owner) is address(0). This happens even if the amount transferred is zero, and the approval update
// is not actually necessary.
// - in ERC20TemporaryAllowance, transfer of 0 value will not update allowance (temporary or persistent)
// therefore the spendAllowance does not revert. However, the transfer of asset will revert because the sender
// is address(0)
const errorName = this.token.temporaryApprove ? 'ERC20InvalidSender' : 'ERC20InvalidApprover';
const value = 0n;
await expect(this.token.connect(this.recipient).transferFrom(ethers.ZeroAddress, this.recipient, value))
.to.be.revertedWithCustomError(this.token, errorName)
.withArgs(ethers.ZeroAddress);
});
});
describe('approve', function () {
beforeEach(function () {
this.approve = (owner, spender, value) => this.token.connect(owner).approve(spender, value);
});
shouldBehaveLikeERC20Approve(initialSupply);
});
}
function shouldBehaveLikeERC20Transfer(balance) {
describe('when the recipient is not the zero address', function () {
it('reverts when the sender does not have enough balance', async function () {
const value = balance + 1n;
await expect(this.transfer(this.holder, this.recipient, value))
.to.be.revertedWithCustomError(this.token, 'ERC20InsufficientBalance')
.withArgs(this.holder, balance, value);
});
describe('when the sender transfers all balance', function () {
const value = balance;
beforeEach(async function () {
this.tx = await this.transfer(this.holder, this.recipient, value);
});
it('transfers the requested value', async function () {
await expect(this.tx).to.changeTokenBalances(this.token, [this.holder, this.recipient], [-value, value]);
});
it('emits a transfer event', async function () {
await expect(this.tx).to.emit(this.token, 'Transfer').withArgs(this.holder, this.recipient, value);
});
});
describe('when the sender transfers zero tokens', function () {
const value = 0n;
beforeEach(async function () {
this.tx = await this.transfer(this.holder, this.recipient, value);
});
it('transfers the requested value', async function () {
await expect(this.tx).to.changeTokenBalances(this.token, [this.holder, this.recipient], [0n, 0n]);
});
it('emits a transfer event', async function () {
await expect(this.tx).to.emit(this.token, 'Transfer').withArgs(this.holder, this.recipient, value);
});
});
});
it('reverts when the recipient is the zero address', async function () {
await expect(this.transfer(this.holder, ethers.ZeroAddress, balance))
.to.be.revertedWithCustomError(this.token, 'ERC20InvalidReceiver')
.withArgs(ethers.ZeroAddress);
});
}
function shouldBehaveLikeERC20Approve(supply) {
describe('when the spender is not the zero address', function () {
describe('when the sender has enough balance', function () {
const value = supply;
it('emits an approval event', async function () {
await expect(this.approve(this.holder, this.recipient, value))
.to.emit(this.token, 'Approval')
.withArgs(this.holder, this.recipient, value);
});
it('approves the requested value when there was no approved value before', async function () {
await this.approve(this.holder, this.recipient, value);
expect(await this.token.allowance(this.holder, this.recipient)).to.equal(value);
});
it('approves the requested value and replaces the previous one when the spender had an approved value', async function () {
await this.approve(this.holder, this.recipient, 1n);
await this.approve(this.holder, this.recipient, value);
expect(await this.token.allowance(this.holder, this.recipient)).to.equal(value);
});
});
describe('when the sender does not have enough balance', function () {
const value = supply + 1n;
it('emits an approval event', async function () {
await expect(this.approve(this.holder, this.recipient, value))
.to.emit(this.token, 'Approval')
.withArgs(this.holder, this.recipient, value);
});
it('approves the requested value when there was no approved value before', async function () {
await this.approve(this.holder, this.recipient, value);
expect(await this.token.allowance(this.holder, this.recipient)).to.equal(value);
});
it('approves the requested value and replaces the previous one when the spender had an approved value', async function () {
await this.approve(this.holder, this.recipient, 1n);
await this.approve(this.holder, this.recipient, value);
expect(await this.token.allowance(this.holder, this.recipient)).to.equal(value);
});
});
});
it('reverts when the spender is the zero address', async function () {
await expect(this.approve(this.holder, ethers.ZeroAddress, supply))
.to.be.revertedWithCustomError(this.token, `ERC20InvalidSpender`)
.withArgs(ethers.ZeroAddress);
});
}
module.exports = {
shouldBehaveLikeERC20,
shouldBehaveLikeERC20Transfer,
shouldBehaveLikeERC20Approve,
};