Switching to Smart Contract Development — Should I Go Deep in Hardhat or Foundry First to Avoid Failing Early Technical Tests?

I onboard juniors pretty regularly, and what actually matters on Day 1 is confidence in a single workflow, not equal knowledge of both. When someone joins our team, they rarely touch deployment scripts immediately — they start by extending tests, debugging traces, and writing small property checks. For this, Foundry tends to give juniors quicker wins because the feedback loop is extremely fast, traces are cleaner, and the cheatcodes help them reason about state transitions.

That said, most production stacks still use Hardhat for at least some part of the lifecycle — especially TypeScript scripts, verification, or mainnet forking with specific plugins. The candidates who perform best in interviews usually pick one tool and go deep enough to build tests beyond the basics: fuzzing inputs, asserting reverts properly, and isolating edge cases. Depth signals readiness. Breadth can come later on the job.

If you want to feel prepared for assessments, start with Foundry tests + one real Hardhat deployment script.

From an audit perspective, Foundry has become almost standard for serious testing work. When teams send us codebases, 70–80% now include at least partial Foundry suites because fuzzing, invariant testing, and differential tests are easier to express. If you plan to work in environments where audits or security reviews matter, Foundry skill shows up immediately — especially your comfort with interpreting traces, gas snapshots, and state-transition edge cases.

However, juniors often underestimate how useful Hardhat scripting is during early job tasks. When protocols ask us to reproduce bugs, deploy PoCs, or run mainnet-fork simulations, we often rely on Hardhat’s plugin ecosystem. So the balance that works in practice is:
Foundry → for testing depth and interview assessments
Hardhat → for tooling interoperability and scripting in real teams

You won’t fail interviews for not knowing both, but lacking Foundry in 2025 does show. Start there, then add minimal Hardhat fluency.

What I actually evaluate during junior interviews is not the tool choice but whether you understand why tests are structured the way they are. Candidates who rely too much on templates — Hardhat or Foundry — struggle when we change constraints in the problem. The strongest juniors demonstrate three things:

1. ability to justify test cases,

2. ability to debug revert reasons cleanly, and

3. ability to modify or extend someone else’s test suite.

Foundry helps because most assessments today revolve around writing or improving tests, not building full dApps. But I’ve hired strong juniors who only knew Hardhat deeply — as long as they wrote clean tests, used mock contracts properly, and understood coverage gaps.

If I were in your position, I’d master Foundry test-writing for interviews and learn Hardhat’s basics for real-world tasks. Showing depth in one → signals readiness; showing confusion across both → signals worry.

I switched from Node.js backend to Solidity last year, and what helped me most was picking one workflow and repeating it until muscle memory formed. I chose Hardhat first because I understood TS scripts better, but I moved to Foundry right before interviews — and that’s what made the difference. Fuzzing + fast test cycles helped me catch mistakes earlier. You don’t need mastery of both; you need mastery of debugging patterns.

Across AOB discussions, the pattern is clear: juniors who go deep into one tool and pair it with strong fundamentals perform much better in early smart contract interviews than those who try to “half-learn” everything.

If you’re planning your next 4–6 weeks, start with our Smart Contract Fundamentals Hub — it maps the core concepts you’ll keep testing with Hardhat or Foundry: https://artofblockchain.club/discussion/smart-contract-fundamentals-hub

Then read how other engineers approach real-world failures in Debugging smart contracts is tough — how do you make it easier? here: https://artofblockchain.club/discussion/debugging-smart-contracts-is-tough-how-do-you-make-it-easier

And if you’re leaning Hardhat-first, this thread on Hardhat debugging mistakes juniors repeat will show you exactly what interviewers and seniors notice in logs, state assumptions, and flaky tests:

https://artofblockchain.club/discussion/need-help-hardhat-debugging-mistakes-juniors-repeat-logs-vs-state-assumptions

Use this thread to ask follow-up questions once you’ve compared your own test suites and scripts with these patterns.