Forking lets you interact with contracts and run tests as if on a real network. Learn how to fork Hedera Testnet on the latest block and test your contracts with the latest state of the network.
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Before you begin, you should be familiar with the following:
To follow along, start with the main branch, which is the default branch of this repository. This gives you the initial state from which you can follow along with the steps as described in the tutorial.
forge manages dependencies by using git submodules. Clone the following project and pass --recurse-submodules to the git clone command to automatically initialize and update the submodule in the repository.
In your terminal, replace the value of "HEX_Encoded_Private_Key" with your ECDSA account's private key in the command below:
Your hex encoded private key must be prefixed with `0x`.
You should see output similar to the following:
Open the Hashscan link to your deployed contract by copying the Deployed to EVM address and replacing <Deployed_Contract_EVM_Address> in the link below:
Example: https://hashscan.io/testnet/contract/0xc1E551Eb1B3430A8D373C43e8804561fca5ce90D
Use Foundry's cast send command to sign and publish a transaction to Hedera Tesnet.
In your terminal, you will need to replace the following items in the command below:
Replace "deployed-contract-EVM-address" with your deployed contracts EVM address
Replace"HEX_Encoded_Private_Key" with your hex encoded private key.
Replace "RPC_URL" with a Tesnet URL.
You should see output similar to the following:
Use cast call to execute TodoList.sol's numberOfTodos().
You should see numberOftodos has incremented by 1.
cast send signs/publishes a transaction and changes the state.
cast call performs a call without changing state. Essentially a read transaction.
An almost-complete test has already been prepared for you. It's located at test/TodoList.t.sol. You will only need to make a few modifications (outlined below) for it to run successfully.
Look for a comment in the code to locate the specific lines of code which you will need to edit. For example, in this step, look for this: // Step (1) in the accompanying tutorial You will need to delete the inline comment that looks like this: /* ... */. Replace it with the correct code.
Open the TodoList.t.sol file and copy and paste the line below.
Replace "Deployed_Contract_EVM_Address" with your deployed contract's EVM address.
This test saves the current number of todos as numberOfTodos, then executes createTodo(), and finally performs an assertion to check that the new number of todos has increased.
Write a statement which asserts that the todoCountAfterCreate is equal to the numberOfTodos + 1.
Copy the below line and paste it in TodoList.t.sol
Using the --fork-url flag you will run your test against a forked Hedera Testnet environment at the latest block.
In your terminal, replace "RPC_URL" with a Tesnet URL
You should see output similar to the following:
Your output will show you the state of numberOfTodos before you created a new todo and after. It also shows whether the test passed, failed or was skipped.
Congratulations, on completing the tutorial on how to fork Hedera Testnet on the latest block.
You have learned how to:
Grab your ECDSA hex encoded private key by logging into .
If you need to create a Hedera account, follow the tutorial.
Next, Replace "RPC_URL" with a Tesnet URL by choosing one of the options over at
Writer: Abi Castro, DevRel Engineer
Editor: Brendan, DevRel Engineer
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