This is the test echidna file that we created to go with the tutorial. There are errors in here on purpose. We're going to refine this smart contract and the finalized version will be submitted in an entirely separate contract

echidna_example.sol

// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity 0.7.6;

import "./GnosisSafe.sol";

contract GnosisSafeTest is GnosisSafe {
    constructor() {
        // Initialize the Gnosis Safe with some owners and a threshold
        address[] memory owners = new address[](3);
        owners[0] = address(0x1);
        owners[1] = address(0x2);
        owners[2] = address(0x3);
        setup(owners, 2, address(0), "", address(0), address(0), 0, address(0));
    }

    // Invariant: Transactions should not be executed without enough signatures
    function echidna_cannot_execute_without_signatures() public returns (bool) {
        // Try executing a transaction with less than the required number of signatures
        bytes memory signatures;
        bool success = execTransaction(address(0x1), 0, "", Enum.Operation.Call, 100000, 0, 0, address(0), payable(address(0)), signatures);
        return !success;
    }

    // Invariant: Nonce must always increase after a transaction
    function echidna_nonce_increases() public returns (bool) {
        uint256 oldNonce = nonce;
        execTransaction(address(0x1), 0, "", Enum.Operation.Call, 100000, 0, 0, address(0), payable(address(0)), "");
        return nonce > oldNonce;
    }

    // Invariant: The contract must have enough gas to execute a transaction
    function echidna_sufficient_gas_for_execution() public returns (bool) {
        uint256 safeTxGas = 100000;
        return gasleft() >= safeTxGas;
    }
}