Writing Multiple Test Cases Together

In this lesson you will learn how to run several test cases together so you can verify a function efficiently. This is for anyone searching for "PHP test cases how to write".

Testing one function against several input patterns at once is called unit testing. Preparing a spread of cases - normal values, boundary values, special values - helps you find bugs early.

The sample code collects several input/expected pairs in the $testCases array and compares add()'s result with the expectation one case at a time using foreach. Notice how $passed counts the successes.

A common stumbling block for beginners is testing only the happy path and forgetting boundary values such as zero or negative numbers. Most real bugs live in exactly those boundary conditions, so include them deliberately.

In real development these tests run automatically every time the code changes, keeping quality steady. Adopting a dedicated framework such as PHPUnit takes this same idea considerably further.

📖 Reference code

<?php
function add($a, $b) {
    return $a + $b;
}

$testCases = [
    ["a" => 2, "b" => 3, "expected" => 5],
    ["a" => -1, "b" => 1, "expected" => 0],
    ["a" => 0, "b" => 0, "expected" => 0],
];

$passed = 0;
foreach ($testCases as $i => $tc) {
    $result = add($tc["a"], $tc["b"]);
    $ok = $result === $tc["expected"];
    if ($ok) $passed++;
    echo "Test " . ($i + 1) . ": " . ($ok ? "OK" : "FAIL") . "\n";
}
echo "{$passed}/" . count($testCases) . " passed";

✍️ Your code

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