Creating an ERC-20 contract

Now that we have ERC-20 in our codebase, lets extend it to create our own ERC-20 contract

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import "forge-std/Script.sol";
import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract MyToken is ERC20 {
    uint256 public number;

    constructor() ERC20("MyToken", "MTK") {}
    function mint(address to, uint256 amount) public {
        _mint(to, amount);
    }
}

Positive tests

Add tests for the standard functions in an ERC-20 contract

test minting
Test transfers
Test approvals

Solution

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import {Test, console} from "forge-std/Test.sol";
import { MyToken } from "../src/Token.sol";

contract CounterTest is Test {
    MyToken public token;

    function setUp() public {
        token = new MyToken();
    }

    function test_Increment() public {
        token.mint(address(this), 100);
        assertEq(token.balanceOf(address(this)), 100);
        token.mint(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
        assertEq(token.balanceOf(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD), 100);
    }

    function test_Transfer() public {
        token.mint(address(this), 100);
        token.transfer(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
        assertEq(token.balanceOf(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD), 100);
        assertEq(token.balanceOf(address(this)), 0);
    }

    function test_Approve() public {
        token.mint(address(this), 100);
        token.approve(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
        uint amount = token.allowance(address(this), 0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD);
        assertEq(amount, 100);
        vm.prank(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD);
        token.transferFrom(address(this), 0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
        assertEq(token.balanceOf(address(this)), 0);
        assertEq(token.balanceOf(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD), 100);
    }
}

Negative tests

Add tests that expect failures

User tries to spend tokens they dont have
User tries to spend on someone elses behalf what they dont have

Solution

function testFail_Mint() public {
    assertEq(token.balanceOf(address(this)), 200);
    token.mint(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
    assertEq(token.balanceOf(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD), 200);
}

function testFail_Transfer() public {
    token.transfer(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
}

function testFail_Allowance() public {
    token.mint(address(this), 100);
    vm.prank(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD);
    token.transferFrom(address(this), 0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD, 100);
    assertEq(token.balanceOf(address(this)), 0);
    assertEq(token.balanceOf(0x075c299cf3b9FCF7C9fD5272cd2ed21A4688bEeD), 100);
}

Class tests

// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.13;

import "forge-std/Test.sol";

import "src/KiratCoin.sol";

contract TestKiratCoin is Test {

    KiratCoin c;

    function setUp() public {
        c = new KiratCoin();
    }

    function testMint() public {
        c.mint(address(this), 100);
        assertEq(c.balanceOf(address(this)), 100 ,"ok");
        assertEq(c.balanceOf(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), uint256(0) ,"ok");

        c.mint(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 100);
        assertEq(c.balanceOf(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), 100, "ok");
    }

    function testTransfer() public {
        c.mint(address(this), 100);
        c.transfer(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 50);

        assertEq(c.balanceOf(address(this)), 50);
        assertEq(c.balanceOf(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), 50);

        vm.prank(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f);
        c.transfer(address(this), 50);

        assertEq(c.balanceOf(address(this)), 100);
        assertEq(c.balanceOf(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), 0);
    }

    function testApprovals() public {
        c.mint(address(this), 100);

        c.approve(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 10);

        assertEq(c.allowance(address(this), 0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), 10);
        assertEq(c.allowance(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, address(this)), 0);

        vm.prank(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f);
        c.transferFrom(address(this), 0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 5);

        assertEq(c.balanceOf(address(this)), 95, "ok");
        assertEq(c.balanceOf(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), 5, "ok");
        assertEq(c.allowance(address(this), 0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f), 5);
    }

    function testFailApprovals() public {
        c.mint(address(this), 100);
        c.approve(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 10);

        vm.prank(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f);
        c.transferFrom(address(this), 0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 100);
    }

    function testFailTransfer() public {
        c.mint(address(this), 20);
        c.transfer(0x587EFaEe4f308aB2795ca35A27Dff8c1dfAF9e3f, 100);
    }

}