How to debug into a forked chain's contract code while running forge test? I do have source code

[sdajklfw389]

I forked an blockchain locally by using vm.createSelectFork. And used forge test --debug to get into the call inside forked contracts.

Basically my test calls different functions on different contracts.

But the problem is: I can debug my test code by solidity code, but i can only step into bytecode of the on-chain contracts.

I do have the source code of the forked contracts and compiled them with the same compiler version/optimizer exactly as the onchain contracts, and I also verified the local runtime bytecode is the same as onchain.

And I have compiled the production code(on-chain contracts) together with my test code. Although my test code only need the interfaces of production code. Not the implementation code.

[adilburaksen]

The debugger shows bytecode for forked contracts because it maps source to compiled artifacts in your out/ directory — not to source files on disk.

You mentioned compiling production code alongside tests but only using interfaces. That's the issue: interfaces don't carry source maps for the implementation. The debugger needs the full implementation artifact with source mappings.

Fix: make sure the full contract implementation (not just the interface) is compiled as part of your forge build:

1. Add the contract source to src/ or lib/ in your project
2. Run forge build — confirm it appears in out/<ContractName>.sol/<ContractName>.json
3. The artifact must contain deployedBytecode.sourceMap — check with jq .deployedBytecode.sourceMap out/ContractName.sol/ContractName.json
4. Run forge test --debug again

Since you've already verified the local bytecode matches on-chain, once the full artifact (with source map) exists in out/, the debugger should resolve it automatically.

If you're importing the contract via a path that resolves to an interface, change the import to point to the full implementation in your test file.