Add PHPUnit for testing

.gitignore

@@ -9,3 +9,7 @@ var/
 
 # Composer dependencies:
 /vendor/
+
+# PHPUnit caches:
+.phpunit.cache/
+.phpunit.result.cache

composer.json

@@ -12,5 +12,7 @@
 			"PHPStarter\\": "src/"
 		}
 	},
-	"require": {}
+	"require-dev": {
+		"phpunit/phpunit": "^12.5"
+	}
 }

phpunit.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.4/phpunit.xsd"
+		 bootstrap="tests/bootstrap.php">
+	<testsuites>
+		<testsuite name="PHPStarter Test Suite">
+			<directory>tests</directory>
+		</testsuite>
+	</testsuites>
+</phpunit>

tests/ExampleTest.php

@@ -0,0 +1,11 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+
+class ExampleTest extends TestCase
+{
+	public function test_it_works()
+	{
+		$this->assertTrue(true);
+	}
+}

tests/bootstrap.php

@@ -0,0 +1,3 @@
+<?php
+
+require __DIR__ . '/../vendor/autoload.php';