Function fuzz_contract_with_calldata 

pub fn fuzz_contract_with_calldata<S: FuzzStateReader>(
    fuzz_state: &S,
    fuzz_fixtures: &FuzzFixtures,
    target: Address,
    func: Function,
) -> impl Strategy<Value = CallDetails> + use<S>

Given a function, it returns a proptest strategy which generates valid abi-encoded calldata for that function’s input types.