diff --git a/tests/ContainerTest.php b/tests/ContainerTest.php
index 389757c..fcff810 100644
--- a/tests/ContainerTest.php
+++ b/tests/ContainerTest.php
@@ -804,7 +804,7 @@ public function __invoke(): ResponseInterface
             }
         };
 
-        $fn = null;
+        $fn = $data = null;
         $fn = #[PHP8] fn(mixed $data = 42) => new Response(200, [], (string) json_encode($data)); // @phpstan-ignore-line
         $container = new Container([
             ResponseInterface::class => $fn,
@@ -1269,17 +1269,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesUnknow
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1301,17 +1293,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesRecurs
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1333,17 +1317,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesString
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class('') {
-            /** @var string */
-            private $data;
-
             public function __construct(string $stdClass)
             {
-                $this->data = $stdClass;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert(is_string($stdClass));
             }
         };
 
@@ -1367,17 +1343,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesVariab
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1402,17 +1370,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesObject
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1435,17 +1395,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesString
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1468,17 +1420,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesIntVar
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1501,17 +1445,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesFloatV
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1534,17 +1470,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesBoolVa
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1567,17 +1495,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesClassN
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1597,17 +1517,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesNullab
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var ?\stdClass */
-            private $data;
-
             public function __construct(?\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1627,17 +1539,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesClassN
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1657,17 +1561,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesClassN
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1687,17 +1583,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesNullab
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var ?\stdClass */
-            private $data;
-
             public function __construct(?\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1717,17 +1605,9 @@ public function testCallableReturnsCallableThatThrowsWhenFactoryReferencesClassM
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class(new \stdClass()) {
-            /** @var \stdClass */
-            private $data;
-
             public function __construct(\stdClass $data)
             {
-                $this->data = $data;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert($data instanceof \stdClass);
             }
         };
 
@@ -1747,17 +1627,9 @@ public function testCallableReturnsCallableThatThrowsWhenConstructorWithoutFacto
         $request = new ServerRequest('GET', 'http://example.com/');
 
         $controller = new class('Alice') {
-            /** @var string */
-            private $data;
-
             public function __construct(string $name)
             {
-                $this->data = $name;
-            }
-
-            public function __invoke(ServerRequestInterface $request): Response
-            {
-                return new Response(200, [], (string) json_encode($this->data));
+                assert(is_string($name));
             }
         };
 
diff --git a/tests/Fixtures/InvalidConstructorIntersection.php b/tests/Fixtures/InvalidConstructorIntersection.php
index 7431cbd..dd2bbc7 100644
--- a/tests/Fixtures/InvalidConstructorIntersection.php
+++ b/tests/Fixtures/InvalidConstructorIntersection.php
@@ -2,6 +2,8 @@
 
 namespace FrameworkX\Tests\Fixtures;
 
+use FrameworkX\Tests\PHP8;
+
 /** PHP 8.1+ **/
 class InvalidConstructorIntersection
 {
diff --git a/tests/Fixtures/InvalidConstructorUnion.php b/tests/Fixtures/InvalidConstructorUnion.php
index 49d0c08..3d8ec64 100644
--- a/tests/Fixtures/InvalidConstructorUnion.php
+++ b/tests/Fixtures/InvalidConstructorUnion.php
@@ -2,6 +2,8 @@
 
 namespace FrameworkX\Tests\Fixtures;
 
+use FrameworkX\Tests\PHP8;
+
 /** PHP 8.0+ **/
 class InvalidConstructorUnion
 {
diff --git a/tests/PHP8.php b/tests/PHP8.php
new file mode 100644
index 0000000..5ee4788
--- /dev/null
+++ b/tests/PHP8.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace FrameworkX\Tests;
+
+/** Dummy attribute used to comment out code for PHP < 8 to ensure compatibility across test matrix */
+#[\Attribute]
+class PHP8
+{
+    public function __construct()
+    {
+        assert(\PHP_VERSION_ID >= 80000);
+    }
+}