Added test cases for "already initialized kernel"

Author: WalterWoshid

tests/Functional/AlreadyInitializedKernelTest.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Okapi\CodeTransformer\Tests\Functional;
+
+use Okapi\CodeTransformer\Tests\Stubs\Kernel\EmptyKernel;
+use Okapi\CodeTransformer\Tests\Stubs\Kernel\ExceptionOnDoubleInitializationKernel;
+use Okapi\CodeTransformer\Tests\Util;
+use Okapi\Singleton\Exceptions\AlreadyInitializedException;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
+use PHPUnit\Framework\TestCase;
+
+#[RunTestsInSeparateProcesses]
+class AlreadyInitializedKernelTest extends TestCase
+{
+    public function testInitializedKernelTwice(): void
+    {
+        Util::clearCache();
+
+        EmptyKernel::init();
+        EmptyKernel::init();
+
+        $this->assertTrue(true);
+    }
+
+    public function testInitializeKernelTwiceWithExceptionOnDoubleInitializationOption(): void
+    {
+        Util::clearCache();
+
+        $this->expectException(AlreadyInitializedException::class);
+
+        ExceptionOnDoubleInitializationKernel::init();
+        ExceptionOnDoubleInitializationKernel::init();
+    }
+}

tests/Stubs/Kernel/EmptyKernel.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Okapi\CodeTransformer\Tests\Stubs\Kernel;
+
+use Okapi\CodeTransformer\CodeTransformerKernel;
+use Okapi\CodeTransformer\Tests\Util;
+
+class EmptyKernel extends CodeTransformerKernel
+{
+    protected ?string $cacheDir = Util::CACHE_DIR;
+
+    protected array $transformers = [];
+}

tests/Stubs/Kernel/ExceptionOnDoubleInitializationKernel.php

@@ -0,0 +1,23 @@
+<?php
+/** @noinspection PhpUnhandledExceptionInspection */
+namespace Okapi\CodeTransformer\Tests\Stubs\Kernel;
+
+use Exception;
+
+class ExceptionOnDoubleInitializationKernel extends EmptyKernel
+{
+    private int $initCount = 0;
+
+    protected bool $throwExceptionOnDoubleInitialization = true;
+
+    protected function preInit(): void
+    {
+        $this->initCount++;
+
+        if ($this->initCount > 1) {
+            throw new Exception('I should not be initialized twice!');
+        }
+
+        parent::preInit();
+    }
+}