Amir of Ekiti

Posted on Jul 8

I Lost $200 Deploying My First Smart Contract — Lessons From a Project Fund Tracker

#web3 #blockchain #learning #ethereum

🚀 My First Web3 Project: A Fund Tracker

Like many developers getting into Web3, I wanted my first project to be more than just a “Hello, Blockchain.” I wanted something useful — something that mimicked real-world use cases.

So I built a Project Fund Tracker.

The idea was simple: contributors could fund a project, and the owner could view and manage the funds. A lightweight version of a crowdfunding contract. It tracked contributions and allowed visibility into total funds collected.

Here’s a basic version of the contribute() function:

function contribute() public payable {
    require(msg.value > 0, "No funds sent");
    contributions[msg.sender] += msg.value;
    totalFunds += msg.value;
}

Everything worked fine:

✅ Contract deployed

✅ Contributions received

✅ State updated

✅ Event logs emitted

Feeling confident — maybe too confident — I decided it was time to go live. I deployed the same contract to Ethereum mainnet and sent 0.1 ETH (~$200) to the contribute() function.

That’s when things broke.

😬 The $200 Mistake

After sending the funds, I checked the contract state.

Nothing had changed.

contributions[msg.sender] was still 0
totalFunds hadn’t increased
No events were emitted

The transaction was marked as successful on Etherscan. Gas was used. ETH was sent.

But it was as if the contract just… ignored it.

🕵️‍♂️ The Debugging Journey

I started retracing my steps.

Here’s what I found:

During a late refactor, I updated the constructor to include default project data like title and owner.
Without realizing it, I also reset totalFunds to zero and unintentionally cleared contribution mappings — right after deployment.
On Sepolia, I had been testing contribute() after the contract had been used a bit. On mainnet, I interacted with it immediately post-deployment, triggering the buggy initialization.

So when I sent ETH, it went in — but the logic to track and emit contribution data was broken. And since I didn’t simulate the full flow on mainnet, I didn’t catch it beforehand.

💡 Lessons Learned

🧪 Sepolia ≠ Mainnet

Testnets are amazing — especially Sepolia. But they don’t simulate everything:

Gas behavior
Timing issues
Real asset risk
Behavioral quirks post-deployment

From now on, I always assume mainnet = production. Period.

🔍 Simulate Everything

Tools like:

Tenderly
Hardhat’s console.log
Foundry’s cast call

…help you simulate transactions and get a dry-run view of what will really happen.

I didn’t simulate the contribute() call after mainnet deployment. If I had, I would’ve caught the problem.

📦 Constructors Can Be Dangerous

The mistake was in the constructor logic.

I hardcoded state initialization in the constructor, assuming it would only run once. It did — but the logic was flawed.

Lesson: treat constructor logic with the same level of scrutiny as any public function. Better yet, use initialize() patterns for safety and transparency.

📉 Emit Logs, Always

Without events, debugging a live contract is like looking for a black cat in a dark room.

I added an event later:

event ContributionReceived(address indexed contributor, uint256 amount);

function contribute() public payable {
    require(msg.value > 0, "No funds sent");

    contributions[msg.sender] += msg.value;
    totalFunds += msg.value;

    emit ContributionReceived(msg.sender, msg.value);
}

Without this, it’s hard to know if a function ran or silently failed. In my case, the lack of logs made it harder to debug what actually happened. The transaction succeeded, gas was consumed, but there was no on-chain evidence of execution — no events, no state changes, nothing obvious to inspect.

⚠️ Sepolia ≠ Mainnet

Sepolia is a great testnet, but it’s not the mainnet. While Sepolia helped me catch most bugs, it didn't replicate all real-world conditions.

Mainnet differs in many ways:

Gas prices fluctuate much more drastically
Miner behavior can affect transaction ordering
Edge cases often appear only in live environments
Stakes are higher — real money is involved

This means passing tests on Sepolia doesn’t guarantee mainnet success. You must simulate mainnet conditions as closely as possible.

✅ The Comeback

After tracking down the issue — mainly an overlooked state reset in the constructor — I:

Refactored the constructor to avoid resetting critical state variables
Added thorough event logging to every public function
Created comprehensive test flows simulating real user interactions on Sepolia
Used simulation tools like Tenderly to analyze transaction behavior
Tested redeployments with a low-balance burner wallet on mainnet

With these safeguards in place, I redeployed to mainnet and finally saw:

Contributions correctly recorded
Event logs emitted as expected
No unexpected state resets or silent failures

This time, the contract worked flawlessly.

🧠 Final Thoughts

Deploying smart contracts to mainnet is like launching a high-stakes product. Mistakes cost real money and trust.

My key takeaways:

Don’t blindly trust testnets — simulate mainnet conditions as much as possible
Use tools to simulate and debug transactions before spending gas
Treat constructor logic with extra caution
Emit detailed events for every state-changing function
Test entire interaction flows, not just isolated functions

💬 Your Turn

Have you ever deployed a contract that worked on testnet but failed on mainnet? Made costly mistakes or discovered helpful tools?

Share your story in the comments — learning from each other helps us all build better, safer Web3 apps.

Thanks for reading! 🙌

If you found this post helpful, please ❤️ or share it with fellow Web3 developers. More stories and lessons coming soon!

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