diff --git a/Classes/Collector/AbstractCollector.php b/Classes/Collector/AbstractCollector.php
index 25736e2..d55c2c7 100644
--- a/Classes/Collector/AbstractCollector.php
+++ b/Classes/Collector/AbstractCollector.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus\Collector;
 
 /*
@@ -14,22 +15,22 @@ abstract class AbstractCollector
     /**
      * @var StorageInterface
      */
-    protected $storage;
+    protected StorageInterface $storage;
 
     /**
      * @var string
      */
-    protected $name;
+    protected string $name;
 
     /**
      * @var string
      */
-    protected $help = '';
+    protected string $help = '';
 
     /**
      * @var array
      */
-    protected $labels = [];
+    protected array $labels = [];
 
     /**
      * @param StorageInterface $storage
diff --git a/Classes/Collector/Counter.php b/Classes/Collector/Counter.php
index 8cb0971..455f37f 100644
--- a/Classes/Collector/Counter.php
+++ b/Classes/Collector/Counter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus\Collector;
 
 /*
@@ -23,7 +24,7 @@ public function getType(): string
     }
 
     /**
-     * @param int|float|double $amount
+     * @param int|float $amount
      * @param array $labels
      */
     public function inc($amount = 1, array $labels = []): void
diff --git a/Classes/Collector/Gauge.php b/Classes/Collector/Gauge.php
index 07be807..656d9b9 100644
--- a/Classes/Collector/Gauge.php
+++ b/Classes/Collector/Gauge.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus\Collector;
 
 /*
@@ -25,7 +26,7 @@ public function getType(): string
     /**
      * Increase the gauge's value
      *
-     * @param int|float|double $amount
+     * @param int|float $amount
      * @param array $labels
      */
     public function inc($amount = 1, array $labels = []): void
@@ -36,7 +37,7 @@ public function inc($amount = 1, array $labels = []): void
     /**
      * Decrease the gauge's value
      *
-     * @param int|float|double $amount
+     * @param int|float $amount
      * @param array $labels
      */
     public function dec($amount = 1, array $labels = []): void
@@ -47,7 +48,7 @@ public function dec($amount = 1, array $labels = []): void
     /**
      * Set the gauge's value
      *
-     * @param int|float|double $value
+     * @param int|float $value
      * @param array $labels
      */
     public function set($value, array $labels = []): void
diff --git a/Classes/CollectorRegistry.php b/Classes/CollectorRegistry.php
index cd64135..83e90ba 100644
--- a/Classes/CollectorRegistry.php
+++ b/Classes/CollectorRegistry.php
@@ -18,17 +18,17 @@ class CollectorRegistry
     /**
      * @var StorageInterface
      */
-    protected $storage;
+    protected StorageInterface $storage;
 
     /**
      * @var array
      */
-    protected $counters = [];
+    protected array $counters = [];
 
     /**
      * @var array
      */
-    protected $gauges = [];
+    protected array $gauges = [];
 
     /**
      * @param StorageInterface $storage
@@ -52,7 +52,7 @@ public function registerMany(array $collectorConfigurations): void
     /**
      * @param string $name
      * @param string $type
-     * @param string|null $help
+     * @param string $help
      * @param array $labels
      * @throws InvalidCollectorTypeException
      */
diff --git a/Classes/Configuration.php b/Classes/Configuration.php
index 7351539..cbdc1b4 100644
--- a/Classes/Configuration.php
+++ b/Classes/Configuration.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus;
 
 /*
@@ -16,17 +17,17 @@ class Configuration
     /**
      * @var string
      */
-    protected $type;
+    protected string $type;
 
     /**
      * @var string
      */
-    protected $help = '';
+    protected string $help = '';
 
     /**
      * @var array
      */
-    protected $labels = [];
+    protected array $labels = [];
 
     /**
      * @param string $type
diff --git a/Classes/DefaultCollectorRegistry.php b/Classes/DefaultCollectorRegistry.php
index 6896718..fc25732 100644
--- a/Classes/DefaultCollectorRegistry.php
+++ b/Classes/DefaultCollectorRegistry.php
@@ -20,7 +20,7 @@ final class DefaultCollectorRegistry extends CollectorRegistry
      * @Flow\InjectConfiguration(path="metrics")
      * @var array
      */
-    protected $settings;
+    protected array $settings = [];
 
     /**
      * @throws Exception\InvalidCollectorTypeException
diff --git a/Classes/Http/MetricsExporterMiddleware.php b/Classes/Http/MetricsExporterMiddleware.php
index 7e1a2a4..6b47bf3 100644
--- a/Classes/Http/MetricsExporterMiddleware.php
+++ b/Classes/Http/MetricsExporterMiddleware.php
@@ -28,17 +28,17 @@ class MetricsExporterMiddleware implements MiddlewareInterface
     /**
      * @var CollectorRegistry
      */
-    protected $collectorRegistry;
+    protected CollectorRegistry $collectorRegistry;
 
     /**
-     * @var LoggerInterface
+     * @var LoggerInterface|null
      */
-    protected $logger;
+    protected ?LoggerInterface $logger = null;
 
     /**
      * @var array
      */
-    protected $options = [
+    protected array $options = [
         'telemetryPath' => '/metrics',
         'basicAuth' => []
     ];
diff --git a/Classes/Renderer.php b/Classes/Renderer.php
index ea2e852..d9591dd 100644
--- a/Classes/Renderer.php
+++ b/Classes/Renderer.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus;
 
 /*
@@ -41,7 +42,7 @@ public function render(array $sampleCollections): string
             }
             $lines[] = '# TYPE ' . $sampleCollection->getName() . " {$sampleCollection->getType()}";
             foreach ($sampleCollection->getSamples() as $sample) {
-                $lines[] = $this->renderSample($sampleCollection, $sample);
+                $lines[] = $this->renderSample($sample);
             }
             $lines[] = '';
         }
@@ -49,11 +50,10 @@ public function render(array $sampleCollections): string
     }
 
     /**
-     * @param SampleCollection $sampleCollection
      * @param Sample $sample
      * @return string
      */
-    private function renderSample(SampleCollection $sampleCollection, Sample $sample): string
+    private function renderSample(Sample $sample): string
     {
         $labelStatements = [];
         foreach ($sample->getLabels() as $labelName => $labelValue) {
diff --git a/Classes/Sample.php b/Classes/Sample.php
index a7d20aa..0c179cd 100644
--- a/Classes/Sample.php
+++ b/Classes/Sample.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus;
 
 /*
@@ -12,15 +13,15 @@ class Sample
     /**
      * @var string
      */
-    private $name;
+    private string $name;
 
     /**
      * @var array
      */
-    private $labels;
+    private array $labels;
 
     /**
-     * @var int|double
+     * @var int|float
      */
     private $value;
 
diff --git a/Classes/SampleCollection.php b/Classes/SampleCollection.php
index 50560ad..5c2da90 100644
--- a/Classes/SampleCollection.php
+++ b/Classes/SampleCollection.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 namespace Flownative\Prometheus;
 
 /*
@@ -12,27 +13,27 @@ class SampleCollection
     /**
      * @var string
      */
-    private $name;
+    private string $name;
 
     /**
      * @var string
      */
-    private $type;
+    private string $type;
 
     /**
      * @var string
      */
-    private $help;
+    private string $help;
 
     /**
      * @var array
      */
-    private $labels;
+    private array $labels;
 
     /**
      * @var Sample[]
      */
-    private $samples = [];
+    private array $samples;
 
     /**
      * @param string $name
diff --git a/Classes/Storage/CounterUpdate.php b/Classes/Storage/CounterUpdate.php
index 9bd7554..620b0f2 100644
--- a/Classes/Storage/CounterUpdate.php
+++ b/Classes/Storage/CounterUpdate.php
@@ -15,19 +15,19 @@ class CounterUpdate
      *
      * @var string
      */
-    private $operation;
+    private string $operation;
 
     /**
      * A positive number
      *
-     * @var int|double|float
+     * @var int|float
      */
     private $value;
 
     /**
      * @var array
      */
-    private $labels;
+    private array $labels;
 
     /**
      * @param string $operation
@@ -40,7 +40,7 @@ public function __construct(string $operation, $value, array $labels)
             throw new \InvalidArgumentException(sprintf('counter update: invalid operation type "%s"', $operation), 1573814341);
         }
         if (!is_numeric($value) || $value < 0) {
-            throw new \InvalidArgumentException(sprintf('invalid value for counter update, must be a positive number'), 1573814397);
+            throw new \InvalidArgumentException('invalid value for counter update, must be a positive number', 1573814397);
         }
         $this->operation = $operation;
         $this->value = $value;
diff --git a/Classes/Storage/GaugeUpdate.php b/Classes/Storage/GaugeUpdate.php
index f0f47bf..3b6aea0 100644
--- a/Classes/Storage/GaugeUpdate.php
+++ b/Classes/Storage/GaugeUpdate.php
@@ -15,19 +15,19 @@ class GaugeUpdate
      *
      * @var string
      */
-    private $operation;
+    private string $operation;
 
     /**
      * A positive number
      *
-     * @var int|double|float
+     * @var int|float
      */
     private $value;
 
     /**
      * @var array
      */
-    private $labels;
+    private array $labels;
 
     /**
      * @param string $operation
@@ -40,7 +40,7 @@ public function __construct(string $operation, $value, array $labels)
             throw new \InvalidArgumentException(sprintf('gauge update: invalid operation type "%s"', $operation), 1574257299);
         }
         if (!is_numeric($value)) {
-            throw new \InvalidArgumentException(sprintf('invalid value for gauge update, must be a number'), 1574257303);
+            throw new \InvalidArgumentException('invalid value for gauge update, must be a number', 1574257303);
         }
         $this->operation = $operation;
         $this->value = $value;
diff --git a/Classes/Storage/InMemoryStorage.php b/Classes/Storage/InMemoryStorage.php
index 63c5758..6ab071d 100644
--- a/Classes/Storage/InMemoryStorage.php
+++ b/Classes/Storage/InMemoryStorage.php
@@ -25,15 +25,16 @@ class InMemoryStorage extends AbstractStorage
     /**
      * @var array
      */
-    private $countersData = [];
+    private array $countersData = [];
 
     /**
      * @var array
      */
-    private $gaugesData = [];
+    private array $gaugesData = [];
 
     /**
      * @return SampleCollection[]
+     * @throws \Exception
      */
     public function collect(): array
     {
@@ -79,6 +80,7 @@ public function registerCollector(AbstractCollector $collector): void
      * @param Counter $counter
      * @param CounterUpdate $update
      * @return void
+     * @throws \Exception
      */
     public function updateCounter(Counter $counter, CounterUpdate $update): void
     {
@@ -102,6 +104,7 @@ public function updateCounter(Counter $counter, CounterUpdate $update): void
      * @param Gauge $gauge
      * @param GaugeUpdate $update
      * @return void
+     * @throws \Exception
      */
     public function updateGauge(Gauge $gauge, GaugeUpdate $update): void
     {
@@ -130,6 +133,7 @@ public function updateGauge(Gauge $gauge, GaugeUpdate $update): void
     /**
      * @param array $collectorsData
      * @return SampleCollection[]
+     * @throws \Exception
      */
     private function prepareCollections(array $collectorsData): array
     {
diff --git a/Classes/Storage/RedisStorage.php b/Classes/Storage/RedisStorage.php
index aeecb2c..0211cad 100644
--- a/Classes/Storage/RedisStorage.php
+++ b/Classes/Storage/RedisStorage.php
@@ -31,57 +31,57 @@ class RedisStorage extends AbstractStorage
     /**
      * @var Counter[]
      */
-    protected $counters;
+    protected array $counters = [];
 
     /**
      * @var Gauge[]
      */
-    protected $gauges;
+    protected array $gauges = [];
 
     /**
      * @var Predis\Client
      */
-    protected $redis;
+    protected Predis\Client $redis;
 
     /**
      * @var string
      */
-    protected $hostname = '127.0.0.1';
+    protected string $hostname = '127.0.0.1';
 
     /**
-     * @var integer
+     * @var int
      */
-    protected $port = 6379;
+    protected int $port = 6379;
 
     /**
      * @var array
      */
-    protected $sentinels = [];
+    protected array $sentinels = [];
 
     /**
      * @var string
      */
-    protected $service = 'mymaster';
+    protected string $service = 'mymaster';
 
     /**
-     * @var integer
+     * @var int
      */
-    protected $database = 0;
+    protected int $database = 0;
 
     /**
      * @var string
      */
-    protected $password = '';
+    protected string $password = '';
 
     /**
      * @var string
      */
-    protected $keyPrefix = 'flownative_prometheus';
+    protected string $keyPrefix = 'flownative_prometheus';
 
     /**
-     * @var boolean
+     * @var bool
      */
-    protected $ignoreConnectionErrors = false;
+    protected bool $ignoreConnectionErrors = false;
 
     /**
      * @param array $options
@@ -321,13 +321,4 @@ private function getRedisClient(): Predis\Client
         }
         return new Predis\Client($connectionParameters, $options);
     }
-
-    /**
-     * @param array $data
-     * @return string
-     */
-    private function toMetricKey(array $data): string
-    {
-        return implode(':', [$this->keyPrefix, $data['type'], $data['name']]);
-    }
 }
diff --git a/Tests/Unit/CollectorRegistryTest.php b/Tests/Unit/CollectorRegistryTest.php
index e74f628..f348eb0 100644
--- a/Tests/Unit/CollectorRegistryTest.php
+++ b/Tests/Unit/CollectorRegistryTest.php
@@ -56,6 +56,7 @@ public function registerManyRegistersCollectorsDefinedInArray(array $collectorCo
     /**
      * @test
      * @throws InvalidCollectorTypeException
+     * @throws \Exception
      */
     public function registerAlsoRegistersCollectorAtStorage(): void
     {
@@ -97,7 +98,7 @@ public function getSampleCollectionsCollectsSamplesFromStorage(): void
         $registry->register('flownative_prometheus_test_calls_total', Counter::TYPE, 'a test call counter', ['tests', 'counter']);
 
         $counterA = $registry->getCounter('flownative_prometheus_test_calls_total');
-        $counterA->inc(1);
+        $counterA->inc();
 
         $sampleCollections = $registry->collect();
 
diff --git a/Tests/Unit/CounterTest.php b/Tests/Unit/CounterTest.php
index 840fa9c..7ac26bc 100644
--- a/Tests/Unit/CounterTest.php
+++ b/Tests/Unit/CounterTest.php
@@ -45,6 +45,7 @@ public function getIdentifierReturnsGeneratedString(): void
 
     /**
      * @test
+     * @throws \Exception
      */
     public function incIncreasesCounterByOne(): void
     {
@@ -77,6 +78,7 @@ public function increaseValues(): array
      * @param $firstValue
      * @param $secondValue
      * @param $expectedResult
+     * @throws \Exception
      */
     public function incIncreasesCounterByGivenValue($firstValue, $secondValue, $expectedResult): void
     {
@@ -94,6 +96,7 @@ public function incIncreasesCounterByGivenValue($firstValue, $secondValue, $expe
 
     /**
      * @test
+     * @throws \Exception
      */
     public function incSupportsLabels(): void
     {
diff --git a/Tests/Unit/DefaultCollectorRegistryTest.php b/Tests/Unit/DefaultCollectorRegistryTest.php
index c6a17d4..92720af 100644
--- a/Tests/Unit/DefaultCollectorRegistryTest.php
+++ b/Tests/Unit/DefaultCollectorRegistryTest.php
@@ -8,7 +8,6 @@
  * (c) Flownative GmbH - www.flownative.com
  */
 
-use Flownative\Prometheus\Collector\Counter;
 use Flownative\Prometheus\DefaultCollectorRegistry;
 use Flownative\Prometheus\Exception\InvalidCollectorTypeException;
 use Flownative\Prometheus\Storage\InMemoryStorage;
@@ -35,7 +34,6 @@ public function collectorsDefinedInSettingsAreRegisteredAutomatically(): void
         $registry->initializeObject();
 
         $counter = $registry->getCounter('flownative_test_hits_total');
-        self::assertInstanceOf(Counter::class, $counter);
         self::assertSame('flownative_test_hits_total', $counter->getName());
     }
 }
diff --git a/Tests/Unit/GaugeTest.php b/Tests/Unit/GaugeTest.php
index 66a5789..a2cbcd5 100644
--- a/Tests/Unit/GaugeTest.php
+++ b/Tests/Unit/GaugeTest.php
@@ -45,6 +45,7 @@ public function getIdentifierReturnsGeneratedString(): void
 
     /**
      * @test
+     * @throws \Exception
      */
     public function incIncreasesGaugeByOne(): void
     {
@@ -78,6 +79,7 @@ public function increaseValues(): array
      * @param $firstValue
      * @param $secondValue
      * @param $expectedResult
+     * @throws \Exception
      */
     public function incIncreasesGaugeByGivenValue($firstValue, $secondValue, $expectedResult): void
     {
@@ -95,6 +97,7 @@ public function incIncreasesGaugeByGivenValue($firstValue, $secondValue, $expect
 
     /**
      * @test
+     * @throws \Exception
      */
     public function decDecreasesGaugeByOne(): void
     {
@@ -112,6 +115,7 @@ public function decDecreasesGaugeByOne(): void
 
     /**
      * @test
+     * @throws \Exception
      */
     public function setSetsTheGaugesValue(): void
     {
@@ -129,6 +133,7 @@ public function setSetsTheGaugesValue(): void
 
     /**
      * @test
+     * @throws \Exception
      */
     public function setToCurrentTimeSetsValueToCurrentUnixTimestamp(): void
     {
@@ -150,6 +155,7 @@ public function setToCurrentTimeSetsValueToCurrentUnixTimestamp(): void
 
     /**
      * @test
+     * @throws \Exception
      */
     public function incSupportsLabels(): void
     {
diff --git a/Tests/Unit/Http/DummyRequestHandler.php b/Tests/Unit/Http/DummyRequestHandler.php
index 8a6390c..b31f5cd 100644
--- a/Tests/Unit/Http/DummyRequestHandler.php
+++ b/Tests/Unit/Http/DummyRequestHandler.php
@@ -18,7 +18,7 @@ class DummyRequestHandler implements RequestHandlerInterface
     /**
      * @var bool
      */
-    protected $handleCalled = false;
+    protected bool $handleCalled = false;
 
     /**
      * @param ServerRequestInterface $request
diff --git a/Tests/Unit/Http/MetricsExporterComponentTest.php b/Tests/Unit/Http/MetricsExporterComponentTest.php
index 36e489a..dd63a98 100644
--- a/Tests/Unit/Http/MetricsExporterComponentTest.php
+++ b/Tests/Unit/Http/MetricsExporterComponentTest.php
@@ -13,9 +13,9 @@
 use Flownative\Prometheus\Exception\InvalidCollectorTypeException;
 use Flownative\Prometheus\Http\MetricsExporterMiddleware;
 use Flownative\Prometheus\Storage\InMemoryStorage;
-use GuzzleHttp\Psr7\Response;
 use GuzzleHttp\Psr7\ServerRequest;
 use GuzzleHttp\Psr7\Uri;
+use Neos\Flow\Security\Exception\AccessDeniedException;
 use Neos\Flow\Tests\UnitTestCase;
 
 class MetricsExporterMiddlewareTest extends UnitTestCase
@@ -25,6 +25,7 @@ class MetricsExporterMiddlewareTest extends UnitTestCase
      */
     public function setUp(): void
     {
+        parent::setUp();
         putenv('FLOWNATIVE_PROMETHEUS_ENABLE=true');
     }
 
@@ -49,6 +50,7 @@ public function middlewareIgnoresRequestsWithNonMatchingPath(): void
     /**
      * @test
      * @throws InvalidCollectorTypeException
+     * @throws AccessDeniedException
      */
     public function middlewareRendersMetrics(): void
     {
@@ -77,6 +79,7 @@ public function middlewareRendersMetrics(): void
 
     /**
      * @test
+     * @throws AccessDeniedException
      */
     public function middlewareRendersCommentIfNoCollectorsAreRegistered(): void
     {
@@ -117,6 +120,7 @@ public function middlewareRendersCommentIfNoMetricsExist(): void
 
     /**
      * @test
+     * @throws AccessDeniedException
      */
     public function telemetryPathIsConfigurable(): void
     {
@@ -137,6 +141,7 @@ public function telemetryPathIsConfigurable(): void
 
     /**
      * @test
+     * @throws AccessDeniedException
      */
     public function middlewareRequiresHttpBasicAuthIfConfigured(): void
     {
@@ -160,6 +165,7 @@ public function middlewareRequiresHttpBasicAuthIfConfigured(): void
 
     /**
      * @test
+     * @throws AccessDeniedException
      */
     public function middlewareAcceptsCorrectHttpBasicAuthIfConfigured(): void
     {
diff --git a/Tests/Unit/Storage/AbstractStorageTest.php b/Tests/Unit/Storage/AbstractStorageTest.php
index f74ffc6..547bf27 100644
--- a/Tests/Unit/Storage/AbstractStorageTest.php
+++ b/Tests/Unit/Storage/AbstractStorageTest.php
@@ -22,7 +22,7 @@ abstract class AbstractStorageTest extends UnitTestCase
     /**
      * @var StorageInterface
      */
-    protected $storage;
+    protected StorageInterface $storage;
 
     /**
      * @test
@@ -116,6 +116,7 @@ public function updateCounterSortsSamplesByLabels(): void
 
     /**
      * @test
+     * @throws \Exception
      */
     public function updateCounterResetsCounterIfSetOperationIsSpecified(): void
     {
diff --git a/Tests/Unit/Storage/RedisStorageTest.php b/Tests/Unit/Storage/RedisStorageTest.php
index 8df498b..40134ff 100644
--- a/Tests/Unit/Storage/RedisStorageTest.php
+++ b/Tests/Unit/Storage/RedisStorageTest.php
@@ -21,9 +21,9 @@ public function setUp(): void
     {
         parent::setUp();
         $this->storage = new RedisStorage([
-            'hostname' => getenv('REDIS_HOST') ?? '127.0.0.1',
-            'port' => getenv('REDIS_PORT') ?? '6379',
-            'password' => getenv('REDIS_PASSWORD') ?? '',
+            'hostname' => getenv('REDIS_HOST') ?: '127.0.0.1',
+            'port' => getenv('REDIS_PORT') ?: '6379',
+            'password' => getenv('REDIS_PASSWORD') ?: '',
         ]);
 
         $this->storage->flush();