The goal of this tutorial is to see what tool could be useful to debug a smart contract using 3 different testing frameworks:
We'll use a functionality of the Cairo language called hints, which allows you to inject python arbitrarily in your code. Hint usage is heavily restricted on StarkNet and is unapplicable in Smart Contracts. But it is extremely useful to debug your contract.
The first smart contract array_contract.cairo
is a dumb smart contract which has a view function that will
- Compute the product of each array element
- Add the current contract’s address to it.
The second smart contract mock_contract.cairo
is also a dumb smart contract which will save an array given at the initialization into a mapping and has a view function that will
- Compute the product of each mapping element
Run the following command in the hardhat directory
npm i
You'll also need cairo-lang
and the starknet-devnet
. To setup a full cairo
env you can take a look at this article
pip install "starknet-devnet>=0.2.1" cairo-lang
You can run any hint on the starknet-devnet if you manage to compile the contract. By default, StarkNet contracts can not use any hints in their code. But An option has been added in hardhat to compile a contract without validating the hints in the contract --disable-hint-validation
. To execute the tests you can run the test
script in package.json
:
To debug a smart contract using hardhat you may want to print variables, there is an example in the smart contract.
The contracts to fix are here.
You can find the test file here.
The following command will run the hardhat tests and execute the hints in this terminal
npm run test
To run the python unit test files you'll need pytest and asynctest
pip install pytest asynctest cairo-lang
The Python testing framework doesn't need to interact with the starknet-devnet
as it can natively use the testing functions from the cairo-lang
package so you can also use any python hint you want. You can even add a breakpoint
in a contract, how powerful is that ? You can run your python unit tests with pytest
and inspect whatever you want in your contract.
The contracts to fix are here.
You can find the test script here
Run the tests separately using:
pytest tests/test_array_contract.py -s -W ignore::DeprecationWarning
pytest tests/test_mock_contract.py -s -W ignore::DeprecationWarning
Or all at once with:
pytest -s -W ignore::DeprecationWarning
To run the ape unit test files you'll need ape configured. This is how you can do it:
pip install eth-ape "starknet.py==0.2.2a0"
ape plugins install cairo starknet
If you start from scratch you'd have to init your project and update the ape-config.yaml
file but here it's already done.
If you want to learn a little bit more about ape here is a video that you can watch which explains the basis of ape for starknet
Since ape hides everything printed by the devnet we can use print
to debug the contract. I chose to save the logs in a file but we could also setup a server that would receive data from the smart-contract execution or whatever other technique you can think of.
To run the tests run the following command:
ape test