OTHER TESTING METHODS

1. Table-Driven Testing

What is it?

Table-driven testing is used when you want to test a single function with multiple sets of predefined inputs and expected outputs in one go. It’s perfect for functions where you know exactly what the output should be for a given input (e.g., a mathematical operation like addition).

Instead of writing 10 separate unit tests for 10 different input combinations, you define all combinations in a “table” (a struct array) and Foundry runs them all.

Why is it useful?

The Catch: Nightly Builds

As mentioned in the transcript, table-driven testing is a relatively new feature. To use it, you need to install Foundry's nightly (cutting-edge) version, not the stable release.

# Install the nightly version of Foundry
foundryup --nightly

How to Write a Table-Driven Test

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

import "forge-std/Test.sol";

// Define a struct to hold one test case: inputs and expected output.
struct TestCase {
    uint256 a;
    uint256 b;
    uint256 expected;
}

contract TableTest is Test {
    // The function under test.
    function sum(uint256 x, uint256 y) public pure returns (uint256) {
        return x + y;
    }

    // This function prepares the "table" of test cases.
    // The `fixture` keyword tells Foundry to run this before the test.
    function testSum_fixture() public pure returns (TestCase[] memory) {
        TestCase[] memory tests = new TestCase[](2);
        tests[0] = TestCase(1, 2, 3); // 1 + 2 should equal 3
        tests[1] = TestCase(10, 20, 30); // 10 + 20 should equal 30
        return tests;
    }

    // The actual test function.
    // Foundry will call this once for each entry in the fixture.
    function testSum(TestCase memory test) public {
        uint256 result = sum(test.a, test.b);
        assertEq(result, test.expected); // Check if result matches expectation
    }
}