Ch 4: Testing

In this chapter, you'll write tests to verify that the ClownBeatdown contract behaves as expected under various scenarios. Testing ensures the functionality, fairness, and access control mechanisms of your contract work seamlessly, particularly in multi-round gameplay. Estimated Time: ~15 minutes.

Getting Started

Navigate to the test folder in your project and open the ClownBeatdown.t.sol file located at:

packages/contracts/test/ClownBeatdown.t.sol

This file is where you'll write all the test cases for the ClownBeatdown contract. Start with the following base code:

// SPDX-License-Identifier: MIT License
pragma solidity ^0.8.13;

import {Test} from "forge-std/Test.sol";
import {ClownBeatdown} from "../src/ClownBeatdown.sol";

contract ClownBeatdownTest is Test {
    ClownBeatdown public clownBeatdown;

    function setUp() public {
        clownBeatdown = new ClownBeatdown(2);
        clownBeatdown.addSecret("Secret A");
        clownBeatdown.addSecret("Secret B");
        clownBeatdown.addSecret("Secret C");
    }
}

The setUp() function initializes the ClownBeatdown contract with a stamina of 2 and adds three secrets to the pool.

Writing Test Cases

Start off with testing the basic functionalities: hit, rob, and reset.

Core functionalities

1. Basic hit functionality

Ensures the clown's stamina decreases when hit.

function test_Hit() public {
    clownBeatdown.hit();
    assertEq(clownBeatdown.getClownStamina(), 1);
}

1. Knockout and rob

Validates that after knocking out the clown, a contributor can rob a valid secret.

function test_KnockoutAndRob() public {
    clownBeatdown.hit();
    clownBeatdown.hit();
    // rob() should return one of the secrets
    bytes memory secret = clownBeatdown.rob();
    assertTrue(
        keccak256(secret) == keccak256(bytes("Secret A")) ||
        keccak256(secret) == keccak256(bytes("Secret B")) ||
        keccak256(secret) == keccak256(bytes("Secret C"))
    );
}

1. Reset functionality

function test_Reset() public {
    clownBeatdown.hit();
    clownBeatdown.hit();
    clownBeatdown.reset();
    assertEq(clownBeatdown.getClownStamina(), 2); // Stamina should be reset to 2
}

1. Secret can change after reset

Validates that secrets returned across rounds are always valid (they may or may not differ depending on randomness).

function test_SecretCanChangeAfterReset() public {
    // Knock out and rob in round 1
    clownBeatdown.hit();
    clownBeatdown.hit();
    bytes memory secret1 = clownBeatdown.rob();

    // Reset and knock out again in round 2
    clownBeatdown.reset();
    clownBeatdown.hit();
    clownBeatdown.hit();
    bytes memory secret2 = clownBeatdown.rob();

    // Both should be valid secrets (they may or may not differ depending on randomness)
    assertTrue(
        keccak256(secret1) == keccak256(bytes("Secret A")) ||
        keccak256(secret1) == keccak256(bytes("Secret B")) ||
        keccak256(secret1) == keccak256(bytes("Secret C"))
    );
    assertTrue(
        keccak256(secret2) == keccak256(bytes("Secret A")) ||
        keccak256(secret2) == keccak256(bytes("Secret B")) ||
        keccak256(secret2) == keccak256(bytes("Secret C"))
    );
}

Now, test for the restrictive/conditional nature of these basic functionalities.

Restricting Actions

1. Preventing hit when clown is down

Ensures that hitting a knocked-out clown is not allowed.

function test_CannotHitWhenDown() public {
    clownBeatdown.hit();
    clownBeatdown.hit();
    vm.expectRevert("CLOWN_ALREADY_DOWN");
    clownBeatdown.hit();
}

1. Preventing rob when clown is standing

Ensures that robbing while the clown still has stamina is not allowed.

function test_CannotRobWhenStanding() public {
    clownBeatdown.hit();
    vm.expectRevert("CLOWN_STILL_STANDING");
    clownBeatdown.rob();
}

1. Preventing reset when clown is standing

Validates that the clown cannot be reset unless it is fully knocked out.

function test_CannotResetWhenStanding() public {
    vm.expectRevert("CLOWN_STILL_STANDING");
    clownBeatdown.reset();
}

Now, test for more complex scenarios.

Complex scenarios

1. Prevent Non-Contributors From Using rob()

Ensures that only contributors in the current round can call rob().

function test_RevertWhen_NonContributorTriesToRob() public {
    address nonContributor = address(0xabcd);

    // Knock out the clown
    clownBeatdown.hit();
    clownBeatdown.hit();

    // Non-contributor should be rejected
    vm.prank(nonContributor);
    vm.expectRevert("NOT_A_CONTRIBUTOR");
    clownBeatdown.rob();

    // Original contributor can still rob
    bytes memory secret = clownBeatdown.rob();
    assertTrue(secret.length > 0);
}

1. Contributor Tracking Across Rounds

Validates that contributions are tracked independently for each round. The test has one contributor knock out the clown in round 1, and a different contributor knock it out in round 2. We check that the round 2 contributor can rob while the round 1 contributor cannot.

function test_ContributorInRound2() public {
    address contributorRound2 = address(0xabcd);

    // Round 1: knocked out by address(this)
    clownBeatdown.hit();
    clownBeatdown.hit();
    bytes memory secret1 = clownBeatdown.rob();
    assertTrue(secret1.length > 0);

    // Reset for round 2
    clownBeatdown.reset();

    // Round 2: knocked out by contributorRound2
    vm.prank(contributorRound2);
    clownBeatdown.hit();
    vm.prank(contributorRound2);
    clownBeatdown.hit();

    // contributorRound2 can rob in round 2
    vm.prank(contributorRound2);
    bytes memory secret2 = clownBeatdown.rob();
    assertTrue(secret2.length > 0);

    // address(this) cannot rob in round 2 (not a contributor this round)
    vm.expectRevert("NOT_A_CONTRIBUTOR");
    clownBeatdown.rob();
}

Test out the file by running the following inside the packages/contracts directory:

sforge build
sforge test

The contract has been tested, time to deploy it!