Sometimes You Need A Hard Hat for Blockchain Testing

Sometimes You Need A Hard Hat for Blockchain Testing

In our labs, we tell the students to use command-line tools wherever possible, and where the terminal or command line should become the natural place to run things.

And so, in cybersecurity, we often avoid those pesky Graphical User Interfaces (GUI) and find a way to drop to a Command Line Interface (CLI). With Ethereum testing, we can use Remix and Ganache, but these take a bit of control away from the user, and are difficult to script with. Here we see Remix being used to test a function in a smart contract [here]:

But there’s another way … the Hardhat way:

With Hardhat, we use command-line tools to create the compilation, testing and deployment of our code. This makes the whole process easier to script and automate. After installing Hardhat, we can check the accounts that it has created for us:

 % npx hardhat accounts 
0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
0x70997970C51812dc3A010C7d01b50e0d17dc79C8
0x3C44CdDdB6a900fa2b585dd299e03d12FA4293BC
0x90F79bf6EB2c4f870365E785982E1f101E93b906
0x15d34AAf54267DB7D7c367839AAf71A00a2C6A65
0x9965507D1a55bcC2695C58ba16FB37d819B0A4dc
0x976EA74026E726554dB657fA54763abd0C3a0aa9
0x14dC79964da2C08b23698B3D3cc7Ca32193d9955

We can then create a new folder and then run Hardhat:

mkdir scrambled
cd scrambled
npx hardhat

This creates a new project for us:

and which contains our project files:

scrambled % ls
README.md        node_modules        scripts
contracts        package-lock.json    test
hardhat.config.js    package.json

The contracts folder is where we put our contracts, and the test folder is where we put our tests. First, let’s add our contract:

cd contacts
rm Greeter.sol
nano scrambled.sol

We then add the following to the contract:

We then compile with:

 % npx hardhat compile
Compiled 1 Solidity file successfully

This shows that our smart contract has been successfully compiled. Now we can go into the test folder, and edit the sample-test.js file:

% cd test
test % ls
sample-test.js
test % nano sample-test.js 

We can now edit this to add the details of the smart contract we have created:

const { ethers } = require("hardhat");

describe("Scrambled", function () {
  it("Just starting it up ...", async function () {
    const sc = await ethers.getContractFactory("Scrambled");
    scram = await sc.deploy();
    await scram.deployed();
    const chall = await scram.scramble();
    console.log(chall);

  });
});

This use Mocha and which is a JavaScript test framework that integrates with Node.js. Our test in this case finds and deploys the “Scrambled” smart contact (using the deploy() method), and then call up the scramble() method. We can then test this method with:

% npx hardhat test


  Scrambled
Find the message from: rmf dwrwnf yd rmf jhrfnhfr, felfcjkiig jh falkhqjhv rmf nkhvf yd kllijckrjyhe, jhxyixfe k owcm qfflfn qfvnff yd lnjxkcg, khq kwrmfhrjckrjyh.

The mapping is:
abcdefghijklmnopqrstuvwxyz
kzcqfdvmjbuiohylsnerwxpagt
    ✔ Just starting it up ... (1271ms)


  1 passing (1s)

Running it again shows a different output (as we select a random phrase each time):

% npx hardhat test  


  Scrambled
Find the message from: jkfn mvfksw, fne yavj tsq zrglebyvge ftyx vd gtbxksw mvfksw htheby jkfn fne hbedebbeq ztsqkqtfe, ky svj leksw behatzeq li eaezfbvskz mvfksw. fne fbtqkfkvsta yiyfegy, fnvrwn, ntme lees tbvrsq dvb nrsqbeqy kd svf fnvrytsqy vd ietby, tsq fihkztaai rye jeaa fbkeq-tsq-feyfeq gezntskygy.

The mapping is:
abcdefghijklmnopqrstuvwxyz
tlzqedwnkpxagsvhubyfrmjcio
    ✔ Just starting it up ... (1504ms)


  1 passing (2s)

And that’s it … cool! Another cool feature is the ability to fallen the smart contact files into one. For this we can use:

npx hardhat flatten

Once ready, we can then create our own blockchain with:

% npx hardhat node    
Started HTTP and WebSocket JSON-RPC server at http://127.0.0.1:8545/

Accounts
========

WARNING: These accounts, and their private keys, are publicly known.
Any funds sent to them on Mainnet or any other live network WILL BE LOST.

Account #0: 0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266 (10000 ETH)
Private Key: 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80

Account #1: 0x70997970c51812dc3a010c7d01b50e0d17dc79c8 (10000 ETH)
Private Key: 0x59c6995e998f97a5a0044966f0945389dc9e86dae88c7a8412f4603b6b78690d

Account #2: 0x3c44cdddb6a900fa2b585dd299e03d12fa4293bc (10000 ETH)
Private Key: 0x5de4111afa1a4b94908f83103eb1f1706367c2e68ca870fc3fb9a804cdab365a

We can now link our application into this service.

Here is the same smart contact, but using Ganach and Remix: