diff --git a/app/config/cache.php b/app/config/cache.php
index 025a0de..903eb3c 100644
--- a/app/config/cache.php
+++ b/app/config/cache.php
@@ -109,8 +109,8 @@ return [
      * ]
      */
     'http_cache' => [
-        'application/json' => '300',
-        'application/zip' => '300',
+        'application/json' => 300,
+        'application/zip' => 300,
     ],
 
 ];
diff --git a/app/src/Middlewares/ThemeMiddleware.php b/app/src/Middlewares/ThemeMiddleware.php
index 6d09faf..a5a37b0 100644
--- a/app/src/Middlewares/ThemeMiddleware.php
+++ b/app/src/Middlewares/ThemeMiddleware.php
@@ -31,14 +31,16 @@ class ThemeMiddleware
     /** Determine the theme from the request. */
     private function getThemeFromRequest(Request $request): string
     {
-        if (! isset($request->getCookieParams()['theme'])) {
+        $cookies = $request->getCookieParams();
+
+        if (! isset($cookies['theme'])) {
             return 'light';
         }
 
-        if (! in_array($request->getCookieParams()['theme'], self::VALID_THEMES)) {
+        if (! in_array($cookies['theme'], self::VALID_THEMES)) {
             return 'light';
         }
 
-        return $request->getCookieParams()['theme'];
+        return $cookies['theme'];
     }
 }
diff --git a/tests/Middlewares/CacheMiddlewareTest.php b/tests/Middlewares/CacheMiddlewareTest.php
new file mode 100644
index 0000000..1e08c4c
--- /dev/null
+++ b/tests/Middlewares/CacheMiddlewareTest.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace Tests\Middlewares;
+
+use App\Middlewares\CacheMiddleware;
+use Fig\Http\Message\StatusCodeInterface;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Slim\Psr7\Headers;
+use Slim\Psr7\Response;
+use Tests\TestCase;
+
+/** @covers \App\Middlewares\CacheMiddleware */
+class CacheMiddlewareTest extends TestCase
+{
+    /** @var RequestHandlerInterface&MockObject */
+    protected $handler;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->request = $this->createMock(ServerRequestInterface::class);
+        $this->handler = $this->createMock(RequestHandlerInterface::class);
+    }
+
+    public function test_it_adds_a_response_cache_header_with_age_of_zero_by_defualt(): void
+    {
+        $this->handler->expects($this->once())->method('handle')->willReturn(
+            new Response(StatusCodeInterface::STATUS_OK, new Headers([
+                'Content-Type' => 'text/html',
+            ]))
+        );
+
+        $response = (new CacheMiddleware($this->config))($this->request, $this->handler);
+
+        $this->assertEquals(['max-age=0, must-revalidate'], $response->getHeader('Cache-Control'));
+    }
+
+    public function test_it_adds_a_response_cache_header_for_a_pre_configured_http_cache_option(): void
+    {
+        $this->handler->expects($this->once())->method('handle')->willReturn(
+            new Response(StatusCodeInterface::STATUS_OK, new Headers([
+                'Content-Type' => 'application/json',
+            ]))
+        );
+
+        $response = (new CacheMiddleware($this->config))($this->request, $this->handler);
+
+        $this->assertEquals(['max-age=300'], $response->getHeader('Cache-Control'));
+    }
+}
diff --git a/tests/Middlewares/ThemeMiddlewareTest.php b/tests/Middlewares/ThemeMiddlewareTest.php
new file mode 100644
index 0000000..1fcb2cc
--- /dev/null
+++ b/tests/Middlewares/ThemeMiddlewareTest.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace Tests\Middlewares;
+
+use App\Middlewares\ThemeMiddleware;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Slim\Views\Twig;
+use Tests\TestCase;
+
+/** @covers \App\Middlewares\ThemeMiddleware */
+class ThemeMiddlewareTest extends TestCase
+{
+    /** @var Twig Twig templating component */
+    protected $view;
+
+    /** @var ServerRequestInterface&MockObject */
+    protected $request;
+
+    /** @var RequestHandlerInterface&MockObject */
+    protected $handler;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->view = $this->container->get(Twig::class);
+        $this->request = $this->createMock(ServerRequestInterface::class);
+        $this->handler = $this->createMock(RequestHandlerInterface::class);
+    }
+
+    public function test_it_sets_the_theme_view_variabe_to_light_by_default(): void
+    {
+        (new ThemeMiddleware($this->view))($this->request, $this->handler);
+
+        $this->assertEquals(['theme' => 'light'], $this->view->getEnvironment()->getGlobals());
+    }
+
+    public function test_it_sets_the_theme_view_variabe_to_dark_when_the_theme_cookie_is_dark(): void
+    {
+        $this->request->expects($this->once())->method('getCookieParams')->willReturn([
+            'theme' => 'dark',
+        ]);
+
+        (new ThemeMiddleware($this->view))($this->request, $this->handler);
+
+        $this->assertEquals(['theme' => 'dark'], $this->view->getEnvironment()->getGlobals());
+    }
+
+    public function test_it_sets_the_theme_view_variabe_to_light_when_the_theme_cookie_is_light(): void
+    {
+        $this->request->expects($this->once())->method('getCookieParams')->willReturn([
+            'theme' => 'dark',
+        ]);
+
+        (new ThemeMiddleware($this->view))($this->request, $this->handler);
+
+        $this->assertEquals(['theme' => 'dark'], $this->view->getEnvironment()->getGlobals());
+    }
+
+    public function test_it_sets_the_theme_view_variabe_to_light_for_an_unknown_value(): void
+    {
+        $this->request->expects($this->once())->method('getCookieParams')->willReturn([
+            'theme' => 'dim',
+        ]);
+
+        (new ThemeMiddleware($this->view))($this->request, $this->handler);
+
+        $this->assertEquals(['theme' => 'light'], $this->view->getEnvironment()->getGlobals());
+    }
+}
diff --git a/tests/TestCase.php b/tests/TestCase.php
index e708c79..2c2e6df 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -22,8 +22,10 @@ class TestCase extends BaseTestCase
     protected $testFilesPath = __DIR__ . '/_files';
 
     /** This method is called before each test. */
-    public function setUp(): void
+    protected function setUp(): void
     {
+        parent::setUp();
+
         Dotenv::createUnsafeImmutable(__DIR__)->safeLoad();
 
         $this->container = BootManager::createContainer(