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yo yo ben zhou
yo yo ben zhou

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Solidity Learning Journey:  Deploying and Testing a Smart Contract

#web3 #blockchain #solidity #ethereum

🚀Previously in My Journey…

In my previous post, I shared why I'm transitioning from SDET to Smart Contract Engineer. I talked about my fascination with Bitcoin's whitepaper, Ethereum's smart contracts, and the revolutionary potential of Web3.
But motivation alone isn't enough - you have to put in the work.
Today, I'm diving into Solidity for the first time, writing, deploying, and testing my first smart contract.

🎯The Plan: A Simple Ethereum Bank

For my first Solidity project, I decided to build a basic Ethereum bank - a contract where users can:

  • 🏦 Deposit ETH into the contract.
  • 💸 Withdraw ETH from the contract.
  • 📊 Keep track of balances (but let Solidity handle the math). Sounds simple, right? Well, things got complicated fast.

🛑 Solidity's First Surprise: Depositing ETH Works Differently Than I Thought

Coming from traditional programming, I assumed I needed a function like this:

function deposit(uint amount) public payable {
    require(amount > 0, "Deposit must be greater than zero");
}
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❌ WRONG Solidity doesn't work like that.The ETH amount is automatically included in msg.value, so no need to pass amount explicitly. A function just needs the payable modifier to receive ETH.

💡 LESSON:Solidity handles ETH transfers at the transaction level, not as function parameters.

💰 Withdrawals and Solidity's Automatic Balance Tracking

Next, I worked on withdrawals, assuming I needed a balance variable. But Solidity already tracks contract balances internally using address(this).balance.
So, instead of:

uint public balance;
balance -= amount;
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I could just let Solidity handle the math and use

payable(msg.sender).transfer(amount);
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💡 LESSON: Solidity is smarter than I thought. You don't need to track balances manually - the blockchain does it for you.

🛠️ Deploying and Testing in Hardhat: "Why Isn't My Contract Deploying?"

I decided to deploy my contract using Hardhat. I wrote a deploy.js script, but then realized:
❌ WRONG. Hardhat tests don't actually use deploy.js.
✅ RIGHT Each test runs on a fresh blockchain state, deploying dynamically.
Still, I ran into errors like:
❌ HH606: Solidity version mismatch → Fixed by updating hardhat.config.js to include solidity version inside.
❌ "Cannot find module 'dotenv'" → Installed missing package (dotenv).
❌ Hardhat compilation issues → Fixed by running:

npx hardhat clean npx hardhat compile
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💡 LESSON: Hardhat automates a lot, but you have to configure Solidity versions correctly to avoid mismatches.

🔥 The Magic of Indexed Events in Solidity

Solidity lets you log transactions with events, which I thought were just for debugging. ❌ WRONG.
✅ Events actually live on the blockchain and make transaction searches super efficient.
For example:
event Deposit(address indexed sender, uint amount);
Indexed parameters make searching logs faster.
Why not use msg.sender directly? Solidity doesn't allow direct global variables in event definitions.

So instead of:

event Deposit(msg.sender, msg.value);
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You write:

event Deposit(address indexed sender, uint amount);
emit Deposit(msg.sender, msg.value);
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💡 LESSON: Events aren't just console logs - they are part of the Ethereum blockchain history.

🔑 Key Takeaways from Day 1

✅ Solidity has built-in ETH balance tracking - no need for manual balance variables.
✅ payable functions automatically receive ETH without an explicit amount parameter.
✅ Hardhat automates testing but requires careful Solidity version configuration.
✅ Events are stored on-chain and indexed makes them searchable.

** 🚀 Next Steps & Future Improvements**

🔹 Add multi-user banking using mapping(address => uint) balances.
🔹 Implement admin-only withdrawals for full contract balance management.
🔹 Deploy SingleUserBank on a public Ethereum testnet.
🔹 Explore gas optimizations and smart contract security best practices.

🌍 Join Me on This Journey!
If you're also learning Solidity, Smart Contracts, or blockchain development, let's connect!
📌GitHub: https://github.com/benzdriver
📌LinkedIn: https://www.linkedin.com/in/ziyan-zhou/
💡 Let’s build the future of blockchain together! 🚀

Top comments (2)

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regisgraptin profile image
Régis •

Hey, wish you good luck on your Solidity journey!
Notice that a smart contract can also receive ETH by using the receive() external payable {}, but still a good practice to have a proper name function as deposit() in your implementation.
I would recommend you to take a look at foundry to write your test in Solidity, instead of switching to typescript, but maybe you are proficient in typescript.
All the best!

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miguelrferreiraf profile image
Miguel Ferreira •

I'm having some difficulties on finding good solidity posts... this is one is very good!