diff --git a/src/Extension/EscaperExtension.php b/src/Extension/EscaperExtension.php
index e09bfeb..7c2c61f 100644
--- a/src/Extension/EscaperExtension.php
+++ b/src/Extension/EscaperExtension.php
@@ -10,8 +10,7 @@
 
 class EscaperExtension implements ExtensionInterface
 {
-    /** @var Escaper */
-    private $escaper;
+    private Escaper $escaper;
 
     public function __construct(?string $encoding = null)
     {
diff --git a/src/Extension/UrlExtension.php b/src/Extension/UrlExtension.php
index aa88637..a4b3cbf 100644
--- a/src/Extension/UrlExtension.php
+++ b/src/Extension/UrlExtension.php
@@ -12,11 +12,9 @@
 
 class UrlExtension implements ExtensionInterface
 {
-    /** @var ServerUrlHelper */
-    private $serverUrlHelper;
+    private ServerUrlHelper $serverUrlHelper;
 
-    /** @var UrlHelper */
-    private $urlHelper;
+    private UrlHelper $urlHelper;
 
     public function __construct(UrlHelper $urlHelper, ServerUrlHelper $serverUrlHelper)
     {
diff --git a/src/PlatesRenderer.php b/src/PlatesRenderer.php
index 46c7b35..bb13084 100644
--- a/src/PlatesRenderer.php
+++ b/src/PlatesRenderer.php
@@ -28,8 +28,7 @@ class PlatesRenderer implements TemplateRendererInterface
 {
     use ArrayParametersTrait;
 
-    /** @var Engine */
-    private $template;
+    private Engine $template;
 
     public function __construct(?Engine $template = null)
     {
diff --git a/test/ConfigProviderTest.php b/test/ConfigProviderTest.php
index 4514895..e11bbbd 100644
--- a/test/ConfigProviderTest.php
+++ b/test/ConfigProviderTest.php
@@ -9,8 +9,7 @@
 
 class ConfigProviderTest extends TestCase
 {
-    /** @var ConfigProvider */
-    private $provider;
+    private ConfigProvider $provider;
 
     protected function setUp(): void
     {
diff --git a/test/Extension/EscaperExtensionTest.php b/test/Extension/EscaperExtensionTest.php
index 4f9d149..98f200f 100644
--- a/test/Extension/EscaperExtensionTest.php
+++ b/test/Extension/EscaperExtensionTest.php
@@ -23,25 +23,30 @@ public function testRegistersEscaperFunctionsWithEngine(): void
 
         $engine = $this->prophesize(Engine::class);
         $engine
-            ->registerFunction('escapeHtml', Argument::that(function ($argument) {
-                return is_array($argument) && $argument[0] instanceof Escaper && $argument[1] === 'escapeHtml';
-            }))->shouldBeCalled();
+            ->registerFunction('escapeHtml', Argument::that(
+                static fn($argument) => is_array($argument) &&
+                    $argument[0] instanceof Escaper && $argument[1] === 'escapeHtml'
+            ))->shouldBeCalled();
         $engine
-            ->registerFunction('escapeHtmlAttr', Argument::that(function ($argument) {
-                return is_array($argument) && $argument[0] instanceof Escaper && $argument[1] === 'escapeHtmlAttr';
-            }))->shouldBeCalled();
+            ->registerFunction('escapeHtmlAttr', Argument::that(
+                static fn($argument) => is_array($argument) &&
+                    $argument[0] instanceof Escaper && $argument[1] === 'escapeHtmlAttr'
+            ))->shouldBeCalled();
         $engine
-            ->registerFunction('escapeJs', Argument::that(function ($argument) {
-                return is_array($argument) && $argument[0] instanceof Escaper && $argument[1] === 'escapeJs';
-            }))->shouldBeCalled();
+            ->registerFunction('escapeJs', Argument::that(
+                static fn($argument) => is_array($argument) &&
+                    $argument[0] instanceof Escaper && $argument[1] === 'escapeJs'
+            ))->shouldBeCalled();
         $engine
-            ->registerFunction('escapeCss', Argument::that(function ($argument) {
-                return is_array($argument) && $argument[0] instanceof Escaper && $argument[1] === 'escapeCss';
-            }))->shouldBeCalled();
+            ->registerFunction('escapeCss', Argument::that(
+                static fn($argument) => is_array($argument) &&
+                    $argument[0] instanceof Escaper && $argument[1] === 'escapeCss'
+            ))->shouldBeCalled();
         $engine
-            ->registerFunction('escapeUrl', Argument::that(function ($argument) {
-                return is_array($argument) && $argument[0] instanceof Escaper && $argument[1] === 'escapeUrl';
-            }))->shouldBeCalled();
+            ->registerFunction('escapeUrl', Argument::that(
+                static fn($argument) => is_array($argument) &&
+                    $argument[0] instanceof Escaper && $argument[1] === 'escapeUrl'
+            ))->shouldBeCalled();
 
         $extension->register($engine->reveal());
     }
diff --git a/test/Extension/UrlExtensionTest.php b/test/Extension/UrlExtensionTest.php
index 04d4a38..61dc2e9 100644
--- a/test/Extension/UrlExtensionTest.php
+++ b/test/Extension/UrlExtensionTest.php
@@ -23,8 +23,7 @@ class UrlExtensionTest extends TestCase
     /** @var ServerUrlHelper|ProphecyInterface */
     private $serverUrlHelper;
 
-    /** @var UrlExtension */
-    private $extension;
+    private UrlExtension $extension;
 
     public function setUp(): void
     {
diff --git a/test/PlatesRendererFactoryTest.php b/test/PlatesRendererFactoryTest.php
index 9eeee5a..1d1eccd 100644
--- a/test/PlatesRendererFactoryTest.php
+++ b/test/PlatesRendererFactoryTest.php
@@ -34,8 +34,7 @@ class PlatesRendererFactoryTest extends TestCase
     /** @var ContainerInterface|ProphecyInterface */
     private $container;
 
-    /** @var bool */
-    private $errorCaught = false;
+    private bool $errorCaught = false;
 
     public function setUp(): void
     {
@@ -184,7 +183,7 @@ public function testExceptionIsRaisedIfMultiplePathsSpecifyDefaultNamespace(): v
         $factory = new PlatesRendererFactory();
 
         // phpcs:ignore WebimpressCodingStandard.NamingConventions.ValidVariableName.NotCamelCaps
-        set_error_handler(function (int $_errno, string $_errstr) {
+        set_error_handler(function (int $_errno, string $_errstr): void {
             $this->errorCaught = true;
         }, E_USER_WARNING);
         $factory($this->container->reveal());
diff --git a/test/PlatesRendererTest.php b/test/PlatesRendererTest.php
index 07d5ba2..fcbfe0d 100644
--- a/test/PlatesRendererTest.php
+++ b/test/PlatesRendererTest.php
@@ -28,11 +28,9 @@ class PlatesRendererTest extends TestCase
 {
     use ProphecyTrait;
 
-    /** @var Engine */
-    private $platesEngine;
+    private Engine $platesEngine;
 
-    /** @var bool */
-    private $error;
+    private bool $error;
 
     public function setUp(): void
     {
@@ -121,7 +119,7 @@ public function testAddingSecondPathWithoutNamespaceIsANoopAndRaisesWarning($ren
         $path  = array_shift($paths);
 
         // phpcs:ignore WebimpressCodingStandard.NamingConventions.ValidVariableName.NotCamelCaps
-        set_error_handler(function (int $_errno, string $message) {
+        set_error_handler(function (int $_errno, string $message): bool {
             $this->error = true;
             $this->assertStringContainsString('duplicate', $message);
             return true;
@@ -250,7 +248,7 @@ public function testAddParameterToOneTemplate(): void
         $this->assertEquals($content, $result);
 
         // phpcs:ignore WebimpressCodingStandard.NamingConventions.ValidVariableName.NotCamelCaps
-        set_error_handler(function (int $_errno, string $message) {
+        set_error_handler(function (int $_errno, string $message): bool {
             $this->assertStringContainsString('Undefined variable: name', $message);
             return true;
         }, E_NOTICE);