Add PHPUnit example

php/phpunit/.envrc

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+use flake "git+https://code.oliverdavies.uk/opdavies/dev-shells#php84"

php/phpunit/.gitignore

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+/.phpunit.cache
+/vendor/

php/phpunit/composer.json

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+{
+    "require-dev": {
+        "phpunit/phpunit": "^12.3"
+    },
+    "autoload": {
+        "psr-4": {
+            "App\\": "src/"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Tests\\": "tests/"
+        }
+    }
+}

php/phpunit/phpunit.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         cacheDirectory=".phpunit.cache"
+         executionOrder="depends,defects"
+         beStrictAboutCoverageMetadata="true"
+         beStrictAboutOutputDuringTests="true"
+         displayDetailsOnPhpunitDeprecations="true"
+         failOnPhpunitDeprecation="true"
+         failOnRisky="true"
+         failOnWarning="true">
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+
+    <source ignoreIndirectDeprecations="true" restrictNotices="true" restrictWarnings="true">
+        <include>
+            <directory>src</directory>
+        </include>
+    </source>
+</phpunit>

php/phpunit/src/Calculator.php

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+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+final class Calculator
+{
+    public function add(int $a, int $b): int
+    {
+        return $a + $b;
+    }
+}

php/phpunit/tests/CalculatorTest.php

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+<?php
+
+declare(strict_types=1);
+
+namespace Tests;
+
+use App\Calculator;
+use PHPUnit\Framework\TestCase;
+
+class CalculatorTest extends TestCase
+{
+    public function test_add(): void
+    {
+        $calculator = new Calculator();
+
+        $this->assertSame(3, $calculator->add(1, 2));
+    }
+}