diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 0a741cf..11b979c 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -461,7 +461,7 @@ jobs:
         with:
           coverage: xdebug
           extensions: intl, zip
-          ini-values: memory_limit=-1, error_reporting=E_ALL, display_errors=On
+          ini-values: memory_limit=-1, error_reporting=E_ALL, display_errors=On, xdebug.mode="develop,coverage"
           php-version: ${{ matrix.php-version }}
           tools: composer
 
diff --git a/src/Config.php b/src/Config.php
index ec17a23..5d03b5b 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -13,6 +13,7 @@
 
 namespace GsTYPO3\CorePatches;
 
+use Composer\Config\ConfigSourceInterface;
 use Composer\Config\JsonConfigSource;
 use Composer\Factory;
 use Composer\Json\JsonFile;
@@ -71,7 +72,7 @@ final class Config implements PersistenceInterface
 
     private JsonFile $jsonFile;
 
-    private JsonConfigSource $jsonConfigSource;
+    private ConfigSourceInterface $configSource;
 
     private Changes $changes;
 
@@ -83,10 +84,12 @@ final class Config implements PersistenceInterface
 
     private Patches $patches;
 
-    public function __construct(?JsonFile $jsonFile = null, ?JsonConfigSource $jsonConfigSource = null)
-    {
+    public function __construct(
+        ?JsonFile $jsonFile = null,
+        ?ConfigSourceInterface $configSource = null
+    ) {
         $this->jsonFile = $jsonFile ?? new JsonFile(Factory::getComposerFile());
-        $this->jsonConfigSource = $jsonConfigSource ?? new JsonConfigSource($this->jsonFile);
+        $this->configSource = $configSource ?? new JsonConfigSource($this->jsonFile);
 
         $this->changes = new Changes();
         $this->preferredInstallChanged = new PreferredInstallChanged();
@@ -165,9 +168,9 @@ public function save(): self
             );
 
             if ($installMethod === '') {
-                $this->jsonConfigSource->removeConfigSetting($name);
+                $this->configSource->removeConfigSetting($name);
             } else {
-                $this->jsonConfigSource->addConfigSetting($name, $installMethod);
+                $this->configSource->addConfigSetting($name, $installMethod);
             }
         }
 
@@ -179,9 +182,9 @@ public function save(): self
         );
 
         if ($this->patches->isEmpty()) {
-            $this->jsonConfigSource->removeProperty($name);
+            $this->configSource->removeProperty($name);
         } else {
-            $this->jsonConfigSource->addProperty($name, $this->patches);
+            $this->configSource->addProperty($name, $this->patches);
         }
 
         // Save plugin configuration
@@ -192,9 +195,9 @@ public function save(): self
         );
 
         if ($this->isEmpty()) {
-            $this->jsonConfigSource->removeProperty($name);
+            $this->configSource->removeProperty($name);
         } else {
-            $this->jsonConfigSource->addProperty($name, $this);
+            $this->configSource->addProperty($name, $this);
         }
 
         // Rewrite configuration to enforce correct formatting
diff --git a/src/Utility/ComposerUtils.php b/src/Utility/ComposerUtils.php
index b95e475..85bff78 100644
--- a/src/Utility/ComposerUtils.php
+++ b/src/Utility/ComposerUtils.php
@@ -48,17 +48,29 @@ final class ComposerUtils
 
     private PatchUtils $patchUtils;
 
-    public function __construct(Composer $composer, IOInterface $io)
-    {
+    public function __construct(
+        Composer $composer,
+        IOInterface $io,
+        ?Config $config = null,
+        ?Application $application = null,
+        ?RestApi $restApi = null,
+        ?PatchUtils $patchUtils = null
+    ) {
         $this->composer = $composer;
         $this->io = $io;
 
-        $this->config = new Config(new JsonFile(Factory::getComposerFile(), null, $this->io));
-        $this->application = new Application();
+        $httpDownloader = Factory::createHttpDownloader($this->io, $this->composer->getConfig());
+
+        $this->config = $config ?? new Config(
+            new JsonFile(Factory::getComposerFile(), $httpDownloader, $this->io),
+            $this->composer->getConfig()->getConfigSource()
+        );
+
+        $this->application = $application ?? new Application();
         $this->application->setAutoExit(false);
 
-        $this->gerritRestApi = new RestApi(Factory::createHttpDownloader($this->io, $this->composer->getConfig()));
-        $this->patchUtils = new PatchUtils($this->composer, $this->io);
+        $this->gerritRestApi = $restApi ?? new RestApi($httpDownloader);
+        $this->patchUtils = $patchUtils ?? new PatchUtils($this->composer, $this->io);
     }
 
     /**
diff --git a/src/Utility/PatchUtils.php b/src/Utility/PatchUtils.php
index 90a4682..fe7dce9 100644
--- a/src/Utility/PatchUtils.php
+++ b/src/Utility/PatchUtils.php
@@ -33,6 +33,16 @@ public function __construct(Composer $composer, IOInterface $io)
         $this->io = $io;
     }
 
+    public function getPatchFileName(string $destination, string $packageName, int $numericId): string
+    {
+        return sprintf(
+            '%s/%s-review-%s.patch',
+            $destination,
+            str_replace('/', '-', $packageName),
+            $numericId
+        );
+    }
+
     public function patchIsPartOfChange(string $patchFileName, int $numericId): bool
     {
         return strpos($patchFileName, '-review-' . $numericId . '.patch') !== false;
@@ -221,12 +231,7 @@ public function save(
 
         foreach ($patches as $packageName => $chunks) {
             $content = implode('', $chunks);
-            $patchFileName = sprintf(
-                '%s/%s-review-%s.patch',
-                $destination,
-                str_replace('/', '-', $packageName),
-                $numericId
-            );
+            $patchFileName = $this->getPatchFileName($destination, $packageName, $numericId);
             $this->io->write(sprintf('  - Creating patch <info>%s</info>', $patchFileName));
             file_put_contents($patchFileName, $content);
             $composerChanges[$packageName] = [$subject => $patchFileName];
diff --git a/tests/Unit/Utility/PatchUtilsTest.php b/tests/Unit/Utility/PatchUtilsTest.php
new file mode 100644
index 0000000..0258708
--- /dev/null
+++ b/tests/Unit/Utility/PatchUtilsTest.php
@@ -0,0 +1,89 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 Core Patches.
+ *
+ * (c) Gilbertsoft LLC (gilbertsoft.org)
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace GsTYPO3\CorePatches\Tests\Unit\Utility;
+
+use Composer\Composer;
+use Composer\Factory;
+use Composer\IO\BufferIO;
+use GsTYPO3\CorePatches\Tests\Unit\TestCase;
+use GsTYPO3\CorePatches\Utility\PatchUtils;
+use RuntimeException;
+
+/**
+ * @covers \GsTYPO3\CorePatches\Utility\PatchUtils
+ */
+final class PatchUtilsTest extends TestCase
+{
+    private string $previousWorkingDir;
+
+    private string $testWorkingDir;
+
+    private BufferIO $bufferIO;
+
+    private Composer $composer;
+
+    private PatchUtils $patchUtils;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        if (($previousWorkingDir = getcwd()) === false) {
+            throw new RuntimeException('Unable to determine current directory.', 1_668_787_261);
+        }
+
+        $this->previousWorkingDir = $previousWorkingDir;
+        $this->testWorkingDir = self::getTestPath();
+        chdir($this->testWorkingDir);
+
+        self::createFiles($this->testWorkingDir, [
+            'composer.json' => 'FIX:composer.json',
+        ]);
+
+        $this->bufferIO = new BufferIO();
+        $this->composer = Factory::create($this->bufferIO);
+
+        $this->patchUtils = new PatchUtils($this->composer, $this->bufferIO);
+    }
+
+    protected function tearDown(): void
+    {
+        chdir($this->previousWorkingDir);
+
+        parent::tearDown();
+    }
+
+    /**
+     * @medium
+     */
+    public function testGetPatchFileName(): void
+    {
+        self::assertSame(
+            'destination/vendor-package-review-12345.patch',
+            $this->patchUtils->getPatchFileName('destination', 'vendor/package', 12345)
+        );
+    }
+
+    /**
+     * @medium
+     */
+    public function testPatchIsPartOfChange(): void
+    {
+        self::assertTrue($this->patchUtils->patchIsPartOfChange(
+            $this->patchUtils->getPatchFileName('destination', 'vendor/package', 12345),
+            12345
+        ));
+        self::assertFalse($this->patchUtils->patchIsPartOfChange('vendor-package.patch', 12345));
+    }
+}