diff --git a/.github/workflows/phpunit.yaml b/.github/workflows/phpunit.yaml
new file mode 100644
index 00000000..1d850685
--- /dev/null
+++ b/.github/workflows/phpunit.yaml
@@ -0,0 +1,36 @@
+name: PHPUnit Tests
+on: [push]
+jobs:
+  run-phpstan:
+    name: Run PHPUnit
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Setup PHP
+      uses: shivammathur/setup-php@v2
+      with:
+        php-version: '8.4'
+        extensions: dom, json, mbstring, psr, xdebug
+        tools: composer:v2
+
+    - name: Check out code
+      uses: actions/checkout@v2
+
+    - name: Get Composer cache directory
+      id: composer-cache
+      run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+
+    - name: Connect downloaded dependencies with a cache in GitHub
+      uses: actions/cache@v3
+      with:
+        path: ${{ steps.composer-cache.outputs.dir }}
+        # Note: Normally, we'd use the composer.lock to generate a hash,
+        # but the lock file is currently not versioned.
+        key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
+        restore-keys: ${{ runner.os }}-composer-
+
+    - name: Install dependencies
+      run: composer install --prefer-dist
+
+    - name: Run PHPUnit
+      run: vendor/bin/phpunit
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..d678ae60
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# PHP Composer files
+composer.lock
+vendor/
+
+# PHPUnit cache
+.phpunit.cache/
diff --git a/Clockwork/Storage/FileStorage.php b/Clockwork/Storage/FileStorage.php
index d0b9ba13..f2098e13 100644
--- a/Clockwork/Storage/FileStorage.php
+++ b/Clockwork/Storage/FileStorage.php
@@ -25,10 +25,10 @@ class FileStorage extends Storage
 	protected $indexHandle;
 
 	// Return new storage, takes path where to store files as argument
-	public function __construct($path, $pathPermissions = 0700, $expiration = null, $compress = false)
+	public function __construct($path, $pathPermissions = null, $expiration = null, $compress = false)
 	{
 		$this->path = $path;
-		$this->pathPermissions = $pathPermissions;
+		$this->pathPermissions = ($pathPermissions === null) ? 0700 : $pathPermissions;
 		$this->expiration = $expiration === null ? 60 * 24 * 7 : $expiration;
 		$this->compress = $compress;
 	}
diff --git a/composer.json b/composer.json
index 80eec482..25a645b4 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,8 @@
     },
     "autoload": {
         "psr-4": {
-            "Clockwork\\": "Clockwork/"
+            "Clockwork\\": "Clockwork/",
+            "Tests\\Clockwork\\": "tests/"
         }
     },
     "extra": {
@@ -37,5 +38,8 @@
                 "Clockwork": "Clockwork\\Support\\Laravel\\Facade"
             }
         }
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^10.0"
     }
 }
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 00000000..0071aabc
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         backupGlobals="false"
+         backupStaticProperties="false"
+         bootstrap="vendor/autoload.php"
+         cacheDirectory=".phpunit.cache"
+         colors="true"
+         displayDetailsOnIncompleteTests="true"
+         displayDetailsOnSkippedTests="true"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerErrors="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
+         displayDetailsOnTestsThatTriggerWarnings="true"
+         failOnWarning="true"
+         processIsolation="false"
+         stopOnFailure="false"
+>
+  <testsuites>
+    <testsuite name="Clockwork Test Suite">
+      <directory>tests</directory>
+    </testsuite>
+  </testsuites>
+  <source>
+    <include>
+      <directory suffix=".php">./src/</directory>
+    </include>
+  </source>
+</phpunit>
diff --git a/tests/Storage/FileStorageTest.php b/tests/Storage/FileStorageTest.php
new file mode 100644
index 00000000..1e9265f3
--- /dev/null
+++ b/tests/Storage/FileStorageTest.php
@@ -0,0 +1,199 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Clockwork\Storage;
+
+use Clockwork\Request\Request;
+use Clockwork\Storage\FileStorage;
+use Clockwork\Storage\StorageInterface;
+use PHPUnit\Framework\TestCase;
+
+class FileStorageTest extends TestCase
+{
+    private const STORAGE_ROOT_DIR = __DIR__ . '/storage';
+    private const STORAGE_PERMISSIONS = 0700;
+    private const STORAGE_EXPIRATION = 10;
+
+    private string $storageDir;
+    private FileStorage $storage;
+
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        $this->storageDir = static::STORAGE_ROOT_DIR . '/' . uniqid();
+
+        $this->storage = new FileStorage(
+            $this->storageDir,
+            static::STORAGE_PERMISSIONS,
+            static::STORAGE_EXPIRATION
+        );
+    }
+
+    public function tearDown(): void
+    {
+        if (file_exists($this->storageDir)) {
+            static::rmdirRecursive($this->storageDir);
+        }
+
+        parent::tearDown();
+    }
+
+    public static function tearDownAfterClass(): void
+    {
+        if (file_exists(static::STORAGE_ROOT_DIR)) {
+            static::rmdirRecursive(static::STORAGE_ROOT_DIR);
+        }
+
+        parent::tearDownAfterClass();
+    }
+
+    private static function rmdirRecursive(string $dir): void
+    {
+        if (!is_dir($dir)) {
+            if (is_file($dir)) {
+                unlink($dir);
+                return;
+            }
+            return;
+        }
+        $iter = dir($dir);
+        while (false !== ($entry = $iter->read())) {
+            if (in_array($entry, ['..', '.'])) {
+                continue;
+            }
+            static::rmdirRecursive($dir . '/' . $entry);
+        }
+        rmdir($dir);
+    }
+
+    public function testInterface(): void
+    {
+        static::assertInstanceOf(StorageInterface::class, $this->storage);
+    }
+
+    public function testStore(): void
+    {
+        $request = new Request([
+            'id' => '12345',
+            'version' => 1,
+            'type' => 'request',
+            'responseDuration' => -12345678.9,
+            'updateToken' => 'abcd1234',
+        ]);
+
+        // ensure the request doesn't exist yet
+        static::assertNull($this->storage->find($request->id));
+
+        // store request
+        $this->storage->store($request);
+
+        // ensure it can be loaded by ID
+        static::assertRequestEquals(
+            $request,
+            $this->storage->find($request->id)
+        );
+
+        // update request
+        $request->addEmail('test', 'nobody@example.com');
+        $this->storage->update($request);
+
+        // ensure it can be loaded by ID
+        static::assertRequestEquals(
+            $request,
+            $this->storage->find($request->id)
+        );
+    }
+
+    public function testCleanup(): void
+    {
+        $now = microtime(true);
+
+        $request1 = new Request([
+            'id' => '12345',
+            'time' => $now - static::STORAGE_EXPIRATION * 60 - 1,
+        ]);
+        $request2 = new Request([
+            'id' => '67890',
+            'time' => $now,
+        ]);
+
+        // store requests
+        // Note: This randomly triggers a cleanup already, so it might be
+        // that request 1 is gone even before we trigger one ourselves.
+        $this->storage->store($request1);
+        $this->storage->store($request2);
+
+        // trigger cleanup
+        $this->storage->cleanup(true);
+
+        // ensure request 1 was purged
+        static::assertNull($this->storage->find($request1->id));
+        // ensure request 2 was kept
+        static::assertNotNull($this->storage->find($request2->id));
+    }
+
+    public function testStore2(): void
+    {
+        $request1 = new Request([
+            'id' => '12345',
+        ]);
+        $request2 = new Request([
+            'id' => '67890',
+        ]);
+
+        // store requests
+        $this->storage->store($request1);
+        $this->storage->store($request2);
+
+        // ensure both can be loaded
+        $allRequests = $this->storage->all();
+        static::assertContainsOnlyInstancesOf(Request::class, $allRequests);
+        static::assertCount(2, $allRequests);
+
+        // ensure both can be loaded by ID
+        static::assertRequestEquals(
+            $request1,
+            $this->storage->find($request1->id)
+        );
+        static::assertRequestEquals(
+            $request2,
+            $this->storage->find($request2->id)
+        );
+
+        // ensure the next after the first is the second
+        $next = $this->storage->next($request1->id);
+        static::assertContainsOnlyInstancesOf(Request::class, $next);
+        static::assertCount(1, $next);
+        static::assertRequestEquals(
+            $request2,
+            $next[0]
+        );
+
+        // ensure the previous before the second is the first
+        $previous = $this->storage->previous($request2->id);
+        static::assertContainsOnlyInstancesOf(Request::class, $previous);
+        static::assertCount(1, $previous);
+        static::assertRequestEquals(
+            $request1,
+            $previous[0]
+        );
+    }
+
+    /**
+     * compare requests
+     *
+     * This ensures that a result is actually a request instance and with
+     * the expected properties.
+     */
+    private static function assertRequestEquals(Request $expected, $actual): void
+    {
+        static::assertInstanceOf(Request::class, $actual);
+
+        $expectedData = array_filter($expected->toArray());
+        $actualData = array_filter($actual->toArray());
+
+        static::assertEquals($expectedData, $actualData);
+    }
+}