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Cheatcodes reference

Some tests require specific setup beyond what is possible using standard flow. Protostar exposes additional functions called cheatcodes that let you modify the state beyond what is normally possible.

Cheatcodes do not require any specific imports or use declarations.

Error handling in cheatcodes​

All cheatcodes return a Result enum:

Result
enum Result<T, felt252> {
    Ok: T,
    Err: E,
}

On successful cheatcode execution, a positive result is returned (OK) - its exact type depends on the cheatcode.

Depending on cheatcode the type of Err may also vary.

Failing test on cheatcode error​

The simplest handling of Result is to unwrap() them. It either returns a cheatcode success value or causes the test to fail entirely:

Simple handling
use result::ResultTrait;

let prepared_contract = prepare(class_hash, @calldata).unwrap();

RevertedTransaction​

Cheatcodes invoke, call, deploy, deploy_contract and deploy_contract_cairo0 and return an Err of type RevertedTransaction in case of failure.

struct RevertedTransaction {
    panic_data: Array::<felt252>, 
}

It also implements a trait:

trait RevertedTransactionTrait {
    fn first(self: @RevertedTransaction) -> felt252;
}

An example handling of RevertedTransaction may look like this

Match handling
match invoke(deployed_contract_address, 'panic_with', @panic_data) {
    Result::Ok(x) => assert(false, 'Shouldnt have succeeded'),
    Result::Err(x) => {
        assert(x.first() == 'error', 'first datum doesnt match');
        assert(*x.panic_data.at(1_u32) == 'data', 'second datum doesnt match');
    }
}

Available cheatcodes​