Owanesh/SSA2324

Code for Security in Software Application course

Security in Software Application

Testing with echidna

According to bestpractices of Echidna, we have a new contract that "wrap" Taxpayer in order to do assertions and testing.

How tests are made

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.22;

import "./Taxpayer.sol";

contract TaxpayerTesting is Taxpayer {
    uint constant ADULT_AGE = 18;
    uint constant ADULT_OLD_AGE = 65;
    Taxpayer alpha;
    Taxpayer bravo;

    constructor() Taxpayer(address(0), address(0)) {
        alpha = new Taxpayer(address(0), address(0));
        bravo = new Taxpayer(address(0), address(0));
        for (uint i = 0; i < ADULT_AGE; i++) {
            alpha.haveBirthday();
            bravo.haveBirthday();
        }
        bravo.marry(address(alpha));
        alpha.marry(address(bravo));
    }
...

Some tests needs to operate on require(<condition>,<reason>) then our approach is to use try{}catch{} statement.

function echidna_block_spawn_of_orphan() public returns (bool) {
    try new Taxpayer(address(1), address(2)) returns (Taxpayer) {
        return false;
    } catch {
        return true;
    }
}

In this case, we want to test that a new Taxpayer cannot be created from two addresses that are not already deployed on blockchain. The condition we are going to test is this

// taxpayer.sol
constructor(address p1, address p2) {
    require(
        (p1 == address(0) && p2 == address(0)) ||
            (Taxpayer(p1).getSpouse() == p2 &&
                Taxpayer(p2).getSpouse() == p1),
        "A new born is allowed only form init and married couple"
    );
    ...
}

So in the test we try to create by passing parent arguments such as address(1), address(2).

Run Echidna

# using brew
brew install echidna
echidna . --contract TaxpayerTesting --config echidna.conf.yaml

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