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Cheatcodes

Often while testing your contract, you want to emulate complex scenarios. As an example, you might want to test how your contract behaves when not authorized contract calls it. Protostar lets you test such scenarios with cheatcodes. In this section, you will learn what cheatcodes are and how to use them to create strong tests for your contracts.

Let's prank a contract​

Assume you want to test a user validation mechanism in your contract. You can leverage start_prank cheatcode to do that. Let's write a simple contract which validates a caller address.

Deployed contract
#[contract]
mod MinimalContract {
    use starknet::get_caller_address;
    use starknet::ContractAddress;
    use starknet::ContractAddressIntoFelt252;
    use traits::Into;
    
    #[external]
    fn is_expected_user() {
        let caller_address = get_caller_address();
        assert(caller_address.into() == 123, 'not authorized');
    }
}

We know from previous section that if we call is_expected_user method, caller_address will be 0. To pass such a test, we have to use start_prank cheatcode. It sets the value returned by get_caller_address() for a targeted contract.

Test
use cheatcodes::RevertedTransactionTrait;
use result::ResultTrait;
use array::ArrayTrait;

#[test]
fn test_invoke_errors() {
    let contract_address = deploy_contract('minimal', @ArrayTrait::new()).unwrap();
    start_prank(123, contract_address);
    invoke(contract_address, 'is_expected_user', @ArrayTrait::new()).unwrap();
}

Such test will pass.

Other cheatcodes​

You can find a list of all available cheatcodes in cheatcode reference