diff --git a/system/Config/Factories.php b/system/Config/Factories.php
index dc74c45e76f7..ab5343d15fb8 100644
--- a/system/Config/Factories.php
+++ b/system/Config/Factories.php
@@ -513,6 +513,12 @@ public static function getBasename(string $alias): string
     /**
      * Gets component data for caching.
      *
+     * @return array{
+     *   options: array<string, bool|string|null>,
+     *   aliases: array<string, class-string>,
+     *   instances: array<class-string, object>,
+     * }
+     *
      * @internal For caching only
      */
     public static function getComponentInstances(string $component): array
diff --git a/system/Test/FilterTestTrait.php b/system/Test/FilterTestTrait.php
index 45411fad0a42..1140adf7dc5e 100644
--- a/system/Test/FilterTestTrait.php
+++ b/system/Test/FilterTestTrait.php
@@ -120,7 +120,7 @@ protected function setUpFilterTestTrait(): void
      * @param FilterInterface|string $filter   The filter instance, class, or alias
      * @param string                 $position "before" or "after"
      *
-     * @phpstan-return Closure(list<string>|null=): mixed
+     * @return Closure(list<string>|null=): mixed
      */
     protected function getFilterCaller($filter, string $position): Closure
     {
@@ -268,6 +268,8 @@ protected function assertFilter(string $route, string $position, string $alias):
      * @param string $route    The route to test
      * @param string $position "before" or "after"
      * @param string $alias    Alias for the anticipated filter
+     *
+     * @return void
      */
     protected function assertNotFilter(string $route, string $position, string $alias)
     {
@@ -286,6 +288,8 @@ protected function assertNotFilter(string $route, string $position, string $alia
      *
      * @param string $route    The route to test
      * @param string $position "before" or "after"
+     *
+     * @return void
      */
     protected function assertHasFilters(string $route, string $position)
     {
@@ -303,6 +307,8 @@ protected function assertHasFilters(string $route, string $position)
      *
      * @param string $route    The route to test
      * @param string $position "before" or "after"
+     *
+     * @return void
      */
     protected function assertNotHasFilters(string $route, string $position)
     {
diff --git a/system/Validation/Validation.php b/system/Validation/Validation.php
index b1b03d211559..f13af5179112 100644
--- a/system/Validation/Validation.php
+++ b/system/Validation/Validation.php
@@ -23,7 +23,6 @@
 use CodeIgniter\HTTP\RequestInterface;
 use CodeIgniter\Validation\Exceptions\ValidationException;
 use CodeIgniter\View\RendererInterface;
-use Config\Validation as ValidationConfig;
 
 /**
  * Validator
@@ -96,7 +95,7 @@ class Validation implements ValidationInterface
     /**
      * Our configuration.
      *
-     * @var ValidationConfig
+     * @var object{ruleSets: list<class-string>}
      */
     protected $config;
 
@@ -110,7 +109,7 @@ class Validation implements ValidationInterface
     /**
      * Validation constructor.
      *
-     * @param ValidationConfig $config
+     * @param object{ruleSets: list<class-string>} $config
      */
     public function __construct($config, RendererInterface $view)
     {
diff --git a/tests/system/API/ResponseTraitTest.php b/tests/system/API/ResponseTraitTest.php
index 978513b74c50..bc61dd06c81d 100644
--- a/tests/system/API/ResponseTraitTest.php
+++ b/tests/system/API/ResponseTraitTest.php
@@ -108,7 +108,7 @@ private function createRequestAndResponse(string $routePath = '', array $userHea
         }
     }
 
-    protected function makeController(string $routePath = '', array $userHeaders = [])
+    protected function makeController(string $routePath = '', array $userHeaders = []): object
     {
         $this->createRequestAndResponse($routePath, $userHeaders);
 
@@ -659,7 +659,7 @@ public function testXMLResponseFormat(): void
         $this->assertSame($xmlFormatter->format($data), $this->response->getXML());
     }
 
-    private function invoke(object $controller, string $method, array $args = [])
+    private function invoke(object $controller, string $method, array $args = []): object
     {
         $method = self::getPrivateMethodInvoker($controller, $method);
 
diff --git a/tests/system/Cache/Handlers/FileHandlerTest.php b/tests/system/Cache/Handlers/FileHandlerTest.php
index 47223198caad..4c45a0712f64 100644
--- a/tests/system/Cache/Handlers/FileHandlerTest.php
+++ b/tests/system/Cache/Handlers/FileHandlerTest.php
@@ -30,7 +30,10 @@ final class FileHandlerTest extends AbstractHandlerTestCase
     private static string $directory = 'FileHandler';
     private Cache $config;
 
-    private static function getKeyArray()
+    /**
+     * @return list<string>
+     */
+    private static function getKeyArray(): array
     {
         return [
             self::$key1,
@@ -328,25 +331,16 @@ public function testSaveMode(int $int, string $string): void
         $this->assertSame($string, $mode);
     }
 
+    /**
+     * @return iterable<int, array{int, numeric-string}>
+     */
     public static function provideSaveMode(): iterable
     {
         return [
-            [
-                0640,
-                '640',
-            ],
-            [
-                0600,
-                '600',
-            ],
-            [
-                0660,
-                '660',
-            ],
-            [
-                0777,
-                '777',
-            ],
+            [0640, '640'],
+            [0600, '600'],
+            [0660, '660'],
+            [0777, '777'],
         ];
     }
 
@@ -382,14 +376,19 @@ public function __construct()
         $this->config->file['storePath'] .= self::$directory;
 
         parent::__construct($this->config);
+
+        helper('filesystem');
     }
 
-    public function getFileInfoTest()
+    /**
+     * @return array<string, bool|int|string>|null
+     */
+    public function getFileInfoTest(): ?array
     {
         $tmpHandle = tmpfile();
         stream_get_meta_data($tmpHandle);
 
-        return $this->getFileInfo(stream_get_meta_data($tmpHandle)['uri'], [
+        return get_file_info(stream_get_meta_data($tmpHandle)['uri'], [
             'name',
             'server_path',
             'size',
diff --git a/tests/system/Cache/Handlers/MemcachedHandlerTest.php b/tests/system/Cache/Handlers/MemcachedHandlerTest.php
index 938607aa9844..c6cfdb8543ee 100644
--- a/tests/system/Cache/Handlers/MemcachedHandlerTest.php
+++ b/tests/system/Cache/Handlers/MemcachedHandlerTest.php
@@ -25,7 +25,10 @@
 #[Group('CacheLive')]
 final class MemcachedHandlerTest extends AbstractHandlerTestCase
 {
-    private static function getKeyArray()
+    /**
+     * @return list<string>
+     */
+    private static function getKeyArray(): array
     {
         return [
             self::$key1,
diff --git a/tests/system/Cache/Handlers/PredisHandlerTest.php b/tests/system/Cache/Handlers/PredisHandlerTest.php
index 9b11c23b0683..4b009582cd55 100644
--- a/tests/system/Cache/Handlers/PredisHandlerTest.php
+++ b/tests/system/Cache/Handlers/PredisHandlerTest.php
@@ -26,7 +26,10 @@ final class PredisHandlerTest extends AbstractHandlerTestCase
 {
     private Cache $config;
 
-    private static function getKeyArray()
+    /**
+     * @return list<string>
+     */
+    private static function getKeyArray(): array
     {
         return [
             self::$key1,
diff --git a/tests/system/Cache/Handlers/RedisHandlerTest.php b/tests/system/Cache/Handlers/RedisHandlerTest.php
index 0eee45f5704f..812985e65e8d 100644
--- a/tests/system/Cache/Handlers/RedisHandlerTest.php
+++ b/tests/system/Cache/Handlers/RedisHandlerTest.php
@@ -28,7 +28,10 @@ final class RedisHandlerTest extends AbstractHandlerTestCase
 {
     private Cache $config;
 
-    private static function getKeyArray()
+    /**
+     * @return list<string>
+     */
+    private static function getKeyArray(): array
     {
         return [
             self::$key1,
diff --git a/tests/system/Commands/CreateDatabaseTest.php b/tests/system/Commands/CreateDatabaseTest.php
index 6bf93f4a2eb3..af5b6d3b1682 100644
--- a/tests/system/Commands/CreateDatabaseTest.php
+++ b/tests/system/Commands/CreateDatabaseTest.php
@@ -64,7 +64,7 @@ private function dropDatabase(): void
         }
     }
 
-    protected function getBuffer()
+    protected function getBuffer(): string
     {
         return $this->getStreamFilterBuffer();
     }
diff --git a/tests/system/Commands/FilterCheckTest.php b/tests/system/Commands/FilterCheckTest.php
index 82826e599d78..6bc594ba1831 100644
--- a/tests/system/Commands/FilterCheckTest.php
+++ b/tests/system/Commands/FilterCheckTest.php
@@ -37,7 +37,7 @@ protected function tearDown(): void
         parent::tearDown();
     }
 
-    protected function getBuffer()
+    protected function getBuffer(): string
     {
         return $this->getStreamFilterBuffer();
     }
diff --git a/tests/system/Commands/HelpCommandTest.php b/tests/system/Commands/HelpCommandTest.php
index 7ce07d8129fb..519f5ab33f65 100644
--- a/tests/system/Commands/HelpCommandTest.php
+++ b/tests/system/Commands/HelpCommandTest.php
@@ -25,7 +25,7 @@ final class HelpCommandTest extends CIUnitTestCase
 {
     use StreamFilterTrait;
 
-    protected function getBuffer()
+    protected function getBuffer(): string
     {
         return $this->getStreamFilterBuffer();
     }
diff --git a/tests/system/Commands/InfoCacheTest.php b/tests/system/Commands/InfoCacheTest.php
index 1c3ad93db5f0..e8cc409356f5 100644
--- a/tests/system/Commands/InfoCacheTest.php
+++ b/tests/system/Commands/InfoCacheTest.php
@@ -41,7 +41,7 @@ protected function tearDown(): void
         config('Cache')->handler = 'file';
     }
 
-    protected function getBuffer()
+    protected function getBuffer(): string
     {
         return $this->getStreamFilterBuffer();
     }
diff --git a/tests/system/Commands/RoutesTest.php b/tests/system/Commands/RoutesTest.php
index 5f3dba1796c1..94455b826826 100644
--- a/tests/system/Commands/RoutesTest.php
+++ b/tests/system/Commands/RoutesTest.php
@@ -40,7 +40,7 @@ protected function tearDown(): void
         parent::tearDown();
     }
 
-    protected function getBuffer()
+    protected function getBuffer(): string
     {
         return str_replace(PHP_EOL, "\n", $this->getStreamFilterBuffer());
     }
diff --git a/tests/system/Commands/Utilities/NamespacesTest.php b/tests/system/Commands/Utilities/NamespacesTest.php
index eea619e1b229..e519ca19d9bc 100644
--- a/tests/system/Commands/Utilities/NamespacesTest.php
+++ b/tests/system/Commands/Utilities/NamespacesTest.php
@@ -42,7 +42,7 @@ protected function tearDown(): void
     /**
      * @see https://regex101.com/r/l3lHfR/1
      */
-    protected function getBuffer()
+    protected function getBuffer(): string
     {
         return preg_replace_callback('/(\|\s*[^|]+\s*\|\s*)(.*?)(\s*\|\s*[^|]+\s*\|)/', static function (array $matches): string {
             $matches[2] = str_replace(DIRECTORY_SEPARATOR, '/', $matches[2]);
diff --git a/tests/system/Config/FactoriesTest.php b/tests/system/Config/FactoriesTest.php
index ed7b15526749..06013e49ca31 100644
--- a/tests/system/Config/FactoriesTest.php
+++ b/tests/system/Config/FactoriesTest.php
@@ -41,7 +41,7 @@ protected function setUp(): void
         Factories::reset();
     }
 
-    protected function getFactoriesStaticProperty(...$params)
+    protected function getFactoriesStaticProperty(...$params): mixed
     {
         // First parameter is the actual property
         $name = array_shift($params);
@@ -425,7 +425,14 @@ public function testDefineAndGet(): void
         $this->assertInstanceOf(EntityModel::class, $model);
     }
 
-    public function testGetComponentInstances()
+    /**
+     * @return array{
+     *   options: array<string, bool|string|null>,
+     *   aliases: array<string, class-string>,
+     *   instances: array<class-string, object>,
+     * }
+     */
+    public function testGetComponentInstances(): array
     {
         Factories::config('App');
         Factories::config(Database::class);
@@ -439,6 +446,19 @@ public function testGetComponentInstances()
         return $data;
     }
 
+    /**
+     * @param array{
+     *   options: array<string, bool|string|null>,
+     *   aliases: array<string, class-string>,
+     *   instances: array<class-string, object>,
+     * } $data
+     *
+     * @return array{
+     *   options: array<string, bool|string|null>,
+     *   aliases: array<string, class-string>,
+     *   instances: array<class-string, object>,
+     * }
+     */
     #[Depends('testGetComponentInstances')]
     public function testSetComponentInstances(array $data)
     {
@@ -456,6 +476,13 @@ public function testSetComponentInstances(array $data)
         return $data;
     }
 
+    /**
+     * @param array{
+     *   options: array<string, bool|string|null>,
+     *   aliases: array<string, class-string>,
+     *   instances: array<class-string, object>,
+     * } $data
+     */
     #[Depends('testSetComponentInstances')]
     public function testIsUpdated(array $data): void
     {
diff --git a/tests/system/Entity/EntityTest.php b/tests/system/Entity/EntityTest.php
index 5f575d67957c..92ed11aa36b6 100644
--- a/tests/system/Entity/EntityTest.php
+++ b/tests/system/Entity/EntityTest.php
@@ -1094,7 +1094,7 @@ public function testJsonSerializableEntity(): void
         $this->assertSame(json_encode($entity->toArray()), json_encode($entity));
     }
 
-    protected function getEntity()
+    private function getEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
@@ -1132,7 +1132,7 @@ public function getFakeBar(): string
         };
     }
 
-    protected function getNewSetterGetterEntity()
+    private function getNewSetterGetterEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
@@ -1178,7 +1178,7 @@ public function _getBar(): string
         };
     }
 
-    protected function getMappedEntity()
+    private function getMappedEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
@@ -1208,7 +1208,7 @@ protected function getSimple(): string
         };
     }
 
-    protected function getSwappedEntity()
+    private function getSwappedEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
@@ -1227,7 +1227,7 @@ protected function getSwappedEntity()
         };
     }
 
-    protected function getSimpleSwappedEntity()
+    private function getSimpleSwappedEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
@@ -1245,7 +1245,7 @@ protected function getSimpleSwappedEntity()
         };
     }
 
-    protected function getCastEntity($data = null): Entity
+    private function getCastEntity($data = null): object
     {
         return new class ($data) extends Entity {
             protected $attributes = [
@@ -1303,7 +1303,7 @@ public function setSeventh(string $seventh): void
         };
     }
 
-    protected function getCastNullableEntity()
+    private function getCastNullableEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
@@ -1332,7 +1332,7 @@ protected function getCastNullableEntity()
         };
     }
 
-    protected function getCustomCastEntity()
+    private function getCustomCastEntity(): object
     {
         return new class () extends Entity {
             protected $attributes = [
diff --git a/tests/system/Filters/fixtures/InvalidClass.php b/tests/system/Filters/fixtures/InvalidClass.php
index 9d727ed1b90f..2cb90e1c571a 100644
--- a/tests/system/Filters/fixtures/InvalidClass.php
+++ b/tests/system/Filters/fixtures/InvalidClass.php
@@ -15,7 +15,7 @@
 
 class InvalidClass
 {
-    public function index()
+    public function index(): string
     {
         return 'bad';
     }
diff --git a/tests/system/HTTP/ContentSecurityPolicyTest.php b/tests/system/HTTP/ContentSecurityPolicyTest.php
index c4e6688ef11f..a9657804f489 100644
--- a/tests/system/HTTP/ContentSecurityPolicyTest.php
+++ b/tests/system/HTTP/ContentSecurityPolicyTest.php
@@ -54,7 +54,7 @@ protected function prepare(bool $CSPEnabled = true): void
         $this->csp = $this->response->getCSP();
     }
 
-    protected function work(string $parm = 'Hello')
+    protected function work(string $parm = 'Hello'): bool
     {
         $body = $parm;
         $this->response->setBody($body);
diff --git a/tests/system/HTTP/Files/FileMovingTest.php b/tests/system/HTTP/Files/FileMovingTest.php
index 2d43c775f949..f0e1564db5b7 100644
--- a/tests/system/HTTP/Files/FileMovingTest.php
+++ b/tests/system/HTTP/Files/FileMovingTest.php
@@ -334,8 +334,7 @@ public function testFailedMoveBecauseOfFalseReturned(): void
  *
  * This overwrite is for testing the move operation.
  */
-
-function is_uploaded_file($filename)
+function is_uploaded_file($filename): bool
 {
     if (! is_file($filename)) {
         file_put_contents($filename, 'data');
@@ -349,8 +348,7 @@ function is_uploaded_file($filename)
  *
  * This overwrite is for testing the move operation.
  */
-
-function move_uploaded_file($filename, $destination, ?bool $setReturnValue = null)
+function move_uploaded_file($filename, $destination, ?bool $setReturnValue = null): bool
 {
     static $return = true;
 
diff --git a/tests/system/RESTful/ResourceControllerTest.php b/tests/system/RESTful/ResourceControllerTest.php
index e51e6c41f694..b7b16325952b 100644
--- a/tests/system/RESTful/ResourceControllerTest.php
+++ b/tests/system/RESTful/ResourceControllerTest.php
@@ -367,7 +367,7 @@ public function testXMLFormatOutput(): void
         $this->assertSame($expected, $result);
     }
 
-    private function invoke(object $controller, string $method, array $args = [])
+    private function invoke(object $controller, string $method, array $args = []): object
     {
         $method = self::getPrivateMethodInvoker($controller, $method);
 
diff --git a/tests/system/Router/RouteCollectionReverseRouteTest.php b/tests/system/Router/RouteCollectionReverseRouteTest.php
index ca70b315f5b6..bc7a30197b88 100644
--- a/tests/system/Router/RouteCollectionReverseRouteTest.php
+++ b/tests/system/Router/RouteCollectionReverseRouteTest.php
@@ -35,7 +35,7 @@ protected function setUp(): void
         $this->resetFactories();
     }
 
-    protected function getCollector(array $config = [], array $files = [], $moduleConfig = null)
+    protected function getCollector(array $config = [], array $files = [], $moduleConfig = null): RouteCollection
     {
         $defaults = [
             'Config' => APPPATH . 'Config',
diff --git a/tests/system/Router/RouteCollectionTest.php b/tests/system/Router/RouteCollectionTest.php
index fbfdb94442b1..6b5270e24fef 100644
--- a/tests/system/Router/RouteCollectionTest.php
+++ b/tests/system/Router/RouteCollectionTest.php
@@ -40,7 +40,7 @@ protected function setUp(): void
         $this->resetFactories();
     }
 
-    protected function getCollector(array $config = [], array $files = [], $moduleConfig = null)
+    protected function getCollector(array $config = [], array $files = [], $moduleConfig = null): RouteCollection
     {
         $defaults = [
             'Config' => APPPATH . 'Config',
diff --git a/tests/system/Session/Handlers/Database/AbstractHandlerTestCase.php b/tests/system/Session/Handlers/Database/AbstractHandlerTestCase.php
index ad27d88bfb76..842824c4a76a 100644
--- a/tests/system/Session/Handlers/Database/AbstractHandlerTestCase.php
+++ b/tests/system/Session/Handlers/Database/AbstractHandlerTestCase.php
@@ -44,7 +44,7 @@ protected function setUp(): void
         }
     }
 
-    abstract protected function getInstance($options = []);
+    abstract protected function getInstance($options = []): DatabaseHandler;
 
     public function testOpen(): void
     {
diff --git a/tests/system/Session/Handlers/Database/MySQLiHandlerTest.php b/tests/system/Session/Handlers/Database/MySQLiHandlerTest.php
index 0b364c7f6559..281ac419c5f5 100644
--- a/tests/system/Session/Handlers/Database/MySQLiHandlerTest.php
+++ b/tests/system/Session/Handlers/Database/MySQLiHandlerTest.php
@@ -32,7 +32,7 @@ protected function setUp(): void
         }
     }
 
-    protected function getInstance($options = [])
+    protected function getInstance($options = []): MySQLiHandler
     {
         $defaults = [
             'driver'            => $this->sessionDriver,
diff --git a/tests/system/Session/Handlers/Database/PostgreHandlerTest.php b/tests/system/Session/Handlers/Database/PostgreHandlerTest.php
index 21fb96b96244..80ec37fbc240 100644
--- a/tests/system/Session/Handlers/Database/PostgreHandlerTest.php
+++ b/tests/system/Session/Handlers/Database/PostgreHandlerTest.php
@@ -32,7 +32,7 @@ protected function setUp(): void
         }
     }
 
-    protected function getInstance($options = [])
+    protected function getInstance($options = []): PostgreHandler
     {
         $defaults = [
             'driver'            => $this->sessionDriver,
diff --git a/tests/system/Session/Handlers/Database/RedisHandlerTest.php b/tests/system/Session/Handlers/Database/RedisHandlerTest.php
index f7e3a5558a13..19efb98cd50d 100644
--- a/tests/system/Session/Handlers/Database/RedisHandlerTest.php
+++ b/tests/system/Session/Handlers/Database/RedisHandlerTest.php
@@ -32,7 +32,7 @@ final class RedisHandlerTest extends CIUnitTestCase
     private string $sessionSavePath = 'tcp://127.0.0.1:6379';
     private string $userIpAddress   = '127.0.0.1';
 
-    protected function getInstance($options = [])
+    protected function getInstance($options = []): RedisHandler
     {
         $defaults = [
             'driver'            => $this->sessionDriver,
diff --git a/tests/system/Session/SessionTest.php b/tests/system/Session/SessionTest.php
index d469c595cd4f..78aec295b718 100644
--- a/tests/system/Session/SessionTest.php
+++ b/tests/system/Session/SessionTest.php
@@ -44,7 +44,7 @@ protected function setUp(): void
         $_SESSION = [];
     }
 
-    protected function getInstance($options = [])
+    protected function getInstance($options = []): MockSession
     {
         $defaults = [
             'driver'            => FileHandler::class,
@@ -209,7 +209,7 @@ public function testGetAsProperty(): void
 
         $session->set('foo', 'bar');
 
-        $this->assertSame('bar', $session->foo);
+        $this->assertSame('bar', $session->foo); // @phpstan-ignore property.notFound
     }
 
     public function testGetAsNormal(): void
@@ -248,7 +248,7 @@ public function testIssetReturnsTrueOnSuccess(): void
         $session->start();
         $_SESSION['foo'] = 'bar';
 
-        $issetReturn = isset($session->foo);
+        $issetReturn = isset($session->foo); // @phpstan-ignore property.notFound
 
         $this->assertTrue($issetReturn);
     }
@@ -259,7 +259,7 @@ public function testIssetReturnsFalseOnNotFound(): void
         $session->start();
         $_SESSION['foo'] = 'bar';
 
-        $issetReturn = isset($session->bar);
+        $issetReturn = isset($session->bar); // @phpstan-ignore property.notFound
 
         $this->assertFalse($issetReturn);
     }
@@ -316,7 +316,7 @@ public function testSetMagicMethod(): void
         $session = $this->getInstance();
         $session->start();
 
-        $session->foo = 'bar';
+        $session->foo = 'bar'; // @phpstan-ignore property.notFound
 
         $this->assertArrayHasKey('foo', $_SESSION);
         $this->assertSame('bar', $_SESSION['foo']);
diff --git a/tests/system/Test/BootstrapFCPATHTest.php b/tests/system/Test/BootstrapFCPATHTest.php
index d58bb847360d..cc03ef99b1b7 100644
--- a/tests/system/Test/BootstrapFCPATHTest.php
+++ b/tests/system/Test/BootstrapFCPATHTest.php
@@ -16,8 +16,6 @@
 use PHPUnit\Framework\Attributes\Group;
 
 /**
- * Class BootstrapFCPATHTest
- *
  * This test confirms that the bootstrap.php
  * will set the correct FCPATH regardless of the current directory
  *
@@ -57,7 +55,7 @@ public function testSetFCPATH(): void
         $this->assertSame($correctPath, $result1);
     }
 
-    private function correctFCPATH()
+    private function correctFCPATH(): string
     {
         return realpath(__DIR__ . '/../../../public') . DIRECTORY_SEPARATOR;
     }
@@ -88,7 +86,7 @@ private function deleteFiles(): void
         }
     }
 
-    private function fileContents()
+    private function fileContents(): string
     {
         $fileContents = '';
         $fileContents .= '<?php' . PHP_EOL;
@@ -99,9 +97,12 @@ private function fileContents()
         $fileContents .= "include_once '" . $this->currentDir . "' . '/../../../system/Test/bootstrap.php';" . PHP_EOL;
         $fileContents .= '// return value of FCPATH' . PHP_EOL;
 
-        return $fileContents . ('echo FCPATH;' . PHP_EOL);
+        return $fileContents . 'echo FCPATH;' . PHP_EOL;
     }
 
+    /**
+     * @return false|string
+     */
     private function readOutput(string $file)
     {
         ob_start();
diff --git a/tests/system/Validation/DatabaseRelatedRulesTest.php b/tests/system/Validation/DatabaseRelatedRulesTest.php
index d683320e968b..1b6445c47f08 100644
--- a/tests/system/Validation/DatabaseRelatedRulesTest.php
+++ b/tests/system/Validation/DatabaseRelatedRulesTest.php
@@ -23,6 +23,13 @@
 #[Group('DatabaseLive')]
 final class DatabaseRelatedRulesTest extends StrictDatabaseRelatedRulesTest
 {
+    /**
+     * @var array{
+     *   ruleSets: list<class-string>,
+     *   groupA: array<string, string>,
+     *   groupA_errors: array<string, array<string, string>>,
+     * }
+     */
     protected array $config = [
         'ruleSets' => [
             Rules::class,
@@ -41,7 +48,7 @@ final class DatabaseRelatedRulesTest extends StrictDatabaseRelatedRulesTest
         ],
     ];
 
-    protected function createRules()
+    protected function createRules(): object
     {
         return new Rules();
     }
diff --git a/tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php b/tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php
index 83f45514682c..43e25d8e7a8a 100644
--- a/tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php
+++ b/tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php
@@ -33,6 +33,14 @@ class DatabaseRelatedRulesTest extends CIUnitTestCase
     use DatabaseTestTrait;
 
     protected Validation $validation;
+
+    /**
+     * @var array{
+     *   ruleSets: list<class-string>,
+     *   groupA: array<string, string>,
+     *   groupA_errors: array<string, array<string, string>>,
+     * }
+     */
     protected array $config = [
         'ruleSets' => [
             Rules::class,
@@ -58,7 +66,7 @@ protected function setUp(): void
         $this->validation->reset();
     }
 
-    protected function createRules()
+    protected function createRules(): object
     {
         return new Rules();
     }
diff --git a/tests/system/Validation/ValidationTest.php b/tests/system/Validation/ValidationTest.php
index 621b20e1103f..0dfe4663fb52 100644
--- a/tests/system/Validation/ValidationTest.php
+++ b/tests/system/Validation/ValidationTest.php
@@ -362,7 +362,7 @@ public function testClosureRuleWithLabel(): void
      *
      * @param mixed $value
      */
-    public function rule1($value)
+    public function rule1($value): bool
     {
         return $value === 'abc';
     }
@@ -394,11 +394,9 @@ public function testCallableRule(): void
     }
 
     /**
-     * Validation rule1
-     *
-     * @param mixed $value
+     * Validation rule2
      */
-    public function rule2($value, array $data, ?string &$error, string $field)
+    public function rule2(mixed $value, array $data, ?string &$error, string $field): bool
     {
         if ($value !== 'abc') {
             $error = 'The ' . $field . ' value is not "abc"';
diff --git a/tests/system/View/ParserPluginTest.php b/tests/system/View/ParserPluginTest.php
index 770bf3afebab..440c0146b393 100644
--- a/tests/system/View/ParserPluginTest.php
+++ b/tests/system/View/ParserPluginTest.php
@@ -138,7 +138,7 @@ public function testValidationErrorsList(): void
         $this->assertSame($this->setHints($this->validator->listErrors()), $this->setHints($this->parser->renderString($template)));
     }
 
-    public function setHints($output)
+    public function setHints(string $output): string
     {
         return preg_replace('/(<!-- DEBUG-VIEW+) (\w+) (\d+)/', '${1}', $output);
     }
diff --git a/utils/phpstan-baseline/argument.type.neon b/utils/phpstan-baseline/argument.type.neon
index 6e6aa7de51fc..7301faeae35d 100644
--- a/utils/phpstan-baseline/argument.type.neon
+++ b/utils/phpstan-baseline/argument.type.neon
@@ -1,4 +1,4 @@
-# total 146 errors
+# total 138 errors
 
 parameters:
     ignoreErrors:
@@ -297,36 +297,6 @@ parameters:
             count: 1
             path: ../../tests/system/Test/TestResponseTest.php
 
-        -
-            message: '#^Parameter \#1 \$config of class CodeIgniter\\Validation\\Validation constructor expects Config\\Validation, stdClass given\.$#'
-            count: 1
-            path: ../../tests/system/Validation/FormatRulesTest.php
-
-        -
-            message: '#^Parameter \#1 \$config of class CodeIgniter\\Validation\\Validation constructor expects Config\\Validation, stdClass given\.$#'
-            count: 1
-            path: ../../tests/system/Validation/RulesTest.php
-
-        -
-            message: '#^Parameter \#1 \$config of class CodeIgniter\\Validation\\Validation constructor expects Config\\Validation, stdClass given\.$#'
-            count: 1
-            path: ../../tests/system/Validation/StrictRules/CreditCardRulesTest.php
-
-        -
-            message: '#^Parameter \#1 \$config of class CodeIgniter\\Validation\\Validation constructor expects Config\\Validation, stdClass given\.$#'
-            count: 1
-            path: ../../tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php
-
-        -
-            message: '#^Parameter \#1 \$config of class CodeIgniter\\Validation\\Validation constructor expects Config\\Validation, stdClass given\.$#'
-            count: 1
-            path: ../../tests/system/Validation/StrictRules/FileRulesTest.php
-
-        -
-            message: '#^Parameter \#1 \$config of class CodeIgniter\\Validation\\Validation constructor expects Config\\Validation, stdClass given\.$#'
-            count: 3
-            path: ../../tests/system/Validation/ValidationTest.php
-
         -
             message: '#^Parameter \#3 \$errors of method CodeIgniter\\Validation\\Validation\:\:check\(\) expects list\<string\>, array\{is_numeric\: ''Nope\. Not a number\.''\} given\.$#'
             count: 1
diff --git a/utils/phpstan-baseline/loader.neon b/utils/phpstan-baseline/loader.neon
index 316b3203b5a8..c715fc07bd3b 100644
--- a/utils/phpstan-baseline/loader.neon
+++ b/utils/phpstan-baseline/loader.neon
@@ -1,4 +1,4 @@
-# total 3334 errors
+# total 3273 errors
 includes:
     - argument.type.neon
     - assign.propertyType.neon
@@ -17,7 +17,6 @@ includes:
     - missingType.iterableValue.neon
     - missingType.parameter.neon
     - missingType.property.neon
-    - missingType.return.neon
     - notIdentical.alwaysTrue.neon
     - nullCoalesce.property.neon
     - offsetAccess.notFound.neon
diff --git a/utils/phpstan-baseline/missingType.iterableValue.neon b/utils/phpstan-baseline/missingType.iterableValue.neon
index 5dfa442af4ab..8ecc1166e8bd 100644
--- a/utils/phpstan-baseline/missingType.iterableValue.neon
+++ b/utils/phpstan-baseline/missingType.iterableValue.neon
@@ -1,4 +1,4 @@
-# total 1582 errors
+# total 1576 errors
 
 parameters:
     ignoreErrors:
@@ -687,11 +687,6 @@ parameters:
             count: 1
             path: ../../system/Config/Factories.php
 
-        -
-            message: '#^Method CodeIgniter\\Config\\Factories\:\:getComponentInstances\(\) return type has no value type specified in iterable type array\.$#'
-            count: 1
-            path: ../../system/Config/Factories.php
-
         -
             message: '#^Method CodeIgniter\\Config\\Factories\:\:getDefinedInstance\(\) has parameter \$arguments with no value type specified in iterable type array\.$#'
             count: 1
@@ -6222,11 +6217,6 @@ parameters:
             count: 1
             path: ../../tests/system/Cache/Handlers/BaseHandlerTest.php
 
-        -
-            message: '#^Method CodeIgniter\\Cache\\Handlers\\FileHandlerTest\:\:provideSaveMode\(\) return type has no value type specified in iterable type iterable\.$#'
-            count: 1
-            path: ../../tests/system/Cache/Handlers/FileHandlerTest.php
-
         -
             message: '#^Method CodeIgniter\\Cache\\ResponseCacheTest\:\:createIncomingRequest\(\) has parameter \$query with no value type specified in iterable type array\.$#'
             count: 1
@@ -6302,16 +6292,6 @@ parameters:
             count: 1
             path: ../../tests/system/Config/DotEnvTest.php
 
-        -
-            message: '#^Method CodeIgniter\\Config\\FactoriesTest\:\:testIsUpdated\(\) has parameter \$data with no value type specified in iterable type array\.$#'
-            count: 1
-            path: ../../tests/system/Config/FactoriesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Config\\FactoriesTest\:\:testSetComponentInstances\(\) has parameter \$data with no value type specified in iterable type array\.$#'
-            count: 1
-            path: ../../tests/system/Config/FactoriesTest.php
-
         -
             message: '#^Method CodeIgniter\\Config\\MimesTest\:\:provideGuessExtensionFromType\(\) return type has no value type specified in iterable type iterable\.$#'
             count: 1
@@ -7327,11 +7307,6 @@ parameters:
             count: 1
             path: ../../tests/system/Validation/CreditCardRulesTest.php
 
-        -
-            message: '#^Property CodeIgniter\\Validation\\DatabaseRelatedRulesTest\:\:\$config type has no value type specified in iterable type array\.$#'
-            count: 1
-            path: ../../tests/system/Validation/DatabaseRelatedRulesTest.php
-
         -
             message: '#^Property CodeIgniter\\Validation\\FileRulesTest\:\:\$config type has no value type specified in iterable type array\.$#'
             count: 1
@@ -7647,11 +7622,6 @@ parameters:
             count: 1
             path: ../../tests/system/Validation/StrictRules/CreditCardRulesTest.php
 
-        -
-            message: '#^Property CodeIgniter\\Validation\\StrictRules\\DatabaseRelatedRulesTest\:\:\$config type has no value type specified in iterable type array\.$#'
-            count: 1
-            path: ../../tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php
-
         -
             message: '#^Property CodeIgniter\\Validation\\StrictRules\\FileRulesTest\:\:\$config type has no value type specified in iterable type array\.$#'
             count: 1
diff --git a/utils/phpstan-baseline/missingType.parameter.neon b/utils/phpstan-baseline/missingType.parameter.neon
index ca934a41eb53..a21867833318 100644
--- a/utils/phpstan-baseline/missingType.parameter.neon
+++ b/utils/phpstan-baseline/missingType.parameter.neon
@@ -1,4 +1,4 @@
-# total 48 errors
+# total 47 errors
 
 parameters:
     ignoreErrors:
@@ -236,8 +236,3 @@ parameters:
             message: '#^Method CodeIgniter\\Session\\SessionTest\:\:getInstance\(\) has parameter \$options with no type specified\.$#'
             count: 1
             path: ../../tests/system/Session/SessionTest.php
-
-        -
-            message: '#^Method CodeIgniter\\View\\ParserPluginTest\:\:setHints\(\) has parameter \$output with no type specified\.$#'
-            count: 1
-            path: ../../tests/system/View/ParserPluginTest.php
diff --git a/utils/phpstan-baseline/missingType.return.neon b/utils/phpstan-baseline/missingType.return.neon
deleted file mode 100644
index 68700bf82235..000000000000
--- a/utils/phpstan-baseline/missingType.return.neon
+++ /dev/null
@@ -1,233 +0,0 @@
-# total 46 errors
-
-parameters:
-    ignoreErrors:
-        -
-            message: '#^Method CodeIgniter\\API\\ResponseTraitTest\:\:invoke\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/API/ResponseTraitTest.php
-
-        -
-            message: '#^Method CodeIgniter\\API\\ResponseTraitTest\:\:makeController\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/API/ResponseTraitTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Cache\\Handlers\\BaseTestFileHandler\:\:getFileInfoTest\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Cache/Handlers/FileHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Cache\\Handlers\\FileHandlerTest\:\:getKeyArray\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Cache/Handlers/FileHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Cache\\Handlers\\MemcachedHandlerTest\:\:getKeyArray\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Cache/Handlers/MemcachedHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Cache\\Handlers\\PredisHandlerTest\:\:getKeyArray\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Cache/Handlers/PredisHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Cache\\Handlers\\RedisHandlerTest\:\:getKeyArray\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Cache/Handlers/RedisHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Commands\\CreateDatabaseTest\:\:getBuffer\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Commands/CreateDatabaseTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Commands\\FilterCheckTest\:\:getBuffer\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Commands/FilterCheckTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Commands\\HelpCommandTest\:\:getBuffer\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Commands/HelpCommandTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Commands\\InfoCacheTest\:\:getBuffer\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Commands/InfoCacheTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Commands\\RoutesTest\:\:getBuffer\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Commands/RoutesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Commands\\Utilities\\NamespacesTest\:\:getBuffer\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Commands/Utilities/NamespacesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Config\\FactoriesTest\:\:getFactoriesStaticProperty\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Config/FactoriesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Config\\FactoriesTest\:\:testGetComponentInstances\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Config/FactoriesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Config\\FactoriesTest\:\:testSetComponentInstances\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Config/FactoriesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getCastNullableEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getCustomCastEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getMappedEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getNewSetterGetterEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getSimpleSwappedEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Entity\\EntityTest\:\:getSwappedEntity\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Entity/EntityTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Filters\\fixtures\\InvalidClass\:\:index\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Filters/fixtures/InvalidClass.php
-
-        -
-            message: '#^Method CodeIgniter\\HTTP\\ContentSecurityPolicyTest\:\:work\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/HTTP/ContentSecurityPolicyTest.php
-
-        -
-            message: '#^Function CodeIgniter\\HTTP\\Files\\is_uploaded_file\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/HTTP/Files/FileMovingTest.php
-
-        -
-            message: '#^Function CodeIgniter\\HTTP\\Files\\move_uploaded_file\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/HTTP/Files/FileMovingTest.php
-
-        -
-            message: '#^Method CodeIgniter\\RESTful\\ResourceControllerTest\:\:invoke\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/RESTful/ResourceControllerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Router\\RouteCollectionReverseRouteTest\:\:getCollector\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Router/RouteCollectionReverseRouteTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Router\\RouteCollectionTest\:\:getCollector\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Router/RouteCollectionTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Session\\Handlers\\Database\\AbstractHandlerTestCase\:\:getInstance\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Session/Handlers/Database/AbstractHandlerTestCase.php
-
-        -
-            message: '#^Method CodeIgniter\\Session\\Handlers\\Database\\MySQLiHandlerTest\:\:getInstance\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Session/Handlers/Database/MySQLiHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Session\\Handlers\\Database\\PostgreHandlerTest\:\:getInstance\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Session/Handlers/Database/PostgreHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Session\\Handlers\\Database\\RedisHandlerTest\:\:getInstance\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Session/Handlers/Database/RedisHandlerTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Session\\SessionTest\:\:getInstance\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Session/SessionTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Test\\BootstrapFCPATHTest\:\:correctFCPATH\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Test/BootstrapFCPATHTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Test\\BootstrapFCPATHTest\:\:fileContents\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Test/BootstrapFCPATHTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Test\\BootstrapFCPATHTest\:\:readOutput\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Test/BootstrapFCPATHTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Test\\FilterTestTraitTest\:\:assertHasFilters\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Test/FilterTestTraitTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Test\\FilterTestTraitTest\:\:assertNotFilter\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Test/FilterTestTraitTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Test\\FilterTestTraitTest\:\:assertNotHasFilters\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Test/FilterTestTraitTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Validation\\DatabaseRelatedRulesTest\:\:createRules\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Validation/DatabaseRelatedRulesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Validation\\StrictRules\\DatabaseRelatedRulesTest\:\:createRules\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Validation/StrictRules/DatabaseRelatedRulesTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Validation\\ValidationTest\:\:rule1\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Validation/ValidationTest.php
-
-        -
-            message: '#^Method CodeIgniter\\Validation\\ValidationTest\:\:rule2\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/Validation/ValidationTest.php
-
-        -
-            message: '#^Method CodeIgniter\\View\\ParserPluginTest\:\:setHints\(\) has no return type specified\.$#'
-            count: 1
-            path: ../../tests/system/View/ParserPluginTest.php