diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 57a0e74..799b016 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -65,4 +65,6 @@ jobs:
 
       - name: Run php-cs-fixer
         if: ${{ matrix.php != '8.2' }} # Not supported yet.
-        run: composer test:syntax
+        run: |
+          composer test:syntax
+          composer test:syntax_tests
diff --git a/composer.json b/composer.json
index 2b164ac..622e205 100644
--- a/composer.json
+++ b/composer.json
@@ -13,9 +13,12 @@
     }
   ],
   "scripts": {
+    "fix:syntax": "./vendor/bin/php-cs-fixer fix ./src --using-cache=no",
+    "fix:syntax_tests": "./vendor/bin/php-cs-fixer fix ./tests --using-cache=no",
     "test:unit": "./vendor/bin/phpunit --color",
     "test:typing": "./vendor/bin/phpstan analyse",
-    "test:syntax": "./vendor/bin/php-cs-fixer fix ./src --dry-run --stop-on-violation --using-cache=no"
+    "test:syntax": "./vendor/bin/php-cs-fixer fix ./src --dry-run --stop-on-violation --using-cache=no",
+    "test:syntax_tests": "./vendor/bin/php-cs-fixer fix ./tests --dry-run --stop-on-violation --using-cache=no"
   },
   "require": {
     "php": ">=8.0",
@@ -39,8 +42,8 @@
     "friendsofphp/php-cs-fixer": "^v3.13.2"
   },
   "autoload": {
-    "psr-4" : {
-      "Minishlink\\WebPush\\" : "src"
+    "psr-4": {
+      "Minishlink\\WebPush\\": "src"
     }
   }
 }
diff --git a/tests/EncryptionTest.php b/tests/EncryptionTest.php
index 59cb109..d53a998 100644
--- a/tests/EncryptionTest.php
+++ b/tests/EncryptionTest.php
@@ -13,15 +13,12 @@
 
 use Base64Url\Base64Url;
 use Jose\Component\Core\JWK;
-use Jose\Component\Core\Util\Ecc\NistCurve;
-use Jose\Component\Core\Util\Ecc\PrivateKey;
-use Jose\Component\KeyManagement\JWKFactory;
 use Minishlink\WebPush\Encryption;
 use Minishlink\WebPush\Utils;
 
 final class EncryptionTest extends PHPUnit\Framework\TestCase
 {
-    public function testDeterministicEncrypt()
+    public function testDeterministicEncrypt(): void
     {
         $contentEncoding = "aes128gcm";
         $plaintext = 'When I grow up, I want to be a watermelon';
@@ -65,7 +62,7 @@ public function testDeterministicEncrypt()
         $this->assertEquals($expected, $result);
     }
 
-    public function testGetContentCodingHeader()
+    public function testGetContentCodingHeader(): void
     {
         $localPublicKey = Base64Url::decode('BP4z9KsN6nGRTbVYI_c7VJSPQTBtkgcy27mlmlMoZIIgDll6e3vCYLocInmYWAmS6TlzAC8wEqKK6PBru3jl7A8');
         $salt = Base64Url::decode('DGv6ra1nlYgDCS1FRnbzlw');
@@ -82,7 +79,7 @@ public function testGetContentCodingHeader()
      *
      * @throws ErrorException
      */
-    public function testPadPayload(string $payload, int $maxLengthToPad, int $expectedResLength)
+    public function testPadPayload(string $payload, int $maxLengthToPad, int $expectedResLength): void
     {
         $res = Encryption::padPayload($payload, $maxLengthToPad, "aesgcm");
 
diff --git a/tests/MessageSentReportTest.php b/tests/MessageSentReportTest.php
index 76797bf..afbba44 100644
--- a/tests/MessageSentReportTest.php
+++ b/tests/MessageSentReportTest.php
@@ -5,118 +5,129 @@
  */
 
 use GuzzleHttp\Psr7\Request;
-use \Minishlink\WebPush\MessageSentReport;
-use \GuzzleHttp\Psr7\Response;
+use GuzzleHttp\Psr7\Response;
+use Minishlink\WebPush\MessageSentReport;
+use PHPUnit\Framework\TestCase;
 
 /**
  * @covers \Minishlink\WebPush\MessageSentReport
  */
-class MessageSentReportTest extends \PHPUnit\Framework\TestCase {
+class MessageSentReportTest extends TestCase
+{
+    /**
+     * @dataProvider generateReportsWithExpiration
+     */
+    public function testIsSubscriptionExpired(MessageSentReport $report, bool $expected): void
+    {
+        $this->assertEquals($expected, $report->isSubscriptionExpired());
+    }
 
-	/**
-	 * @dataProvider generateReportsWithExpiration
-	 */
-	public function testIsSubscriptionExpired(MessageSentReport $report, bool $expected): void {
-		$this->assertEquals($expected, $report->isSubscriptionExpired());
-	}
-
-	public function generateReportsWithExpiration(): array {
-	    $request = new Request('POST', 'https://example.com');
-		return [
-			[new MessageSentReport($request, new Response(404)), true],
-			[new MessageSentReport($request, new Response(410)), true],
-			[new MessageSentReport($request, new Response(500)), false],
-			[new MessageSentReport($request, new Response(200)), false]
-		];
-	}
+    public function generateReportsWithExpiration(): array
+    {
+        $request = new Request('POST', 'https://example.com');
+        return [
+            [new MessageSentReport($request, new Response(404)), true],
+            [new MessageSentReport($request, new Response(410)), true],
+            [new MessageSentReport($request, new Response(500)), false],
+            [new MessageSentReport($request, new Response(200)), false]
+        ];
+    }
 
-	/**
-	 * @dataProvider generateReportsWithEndpoints
-	 */
-	public function testGetEndpoint(MessageSentReport $report, string $expected): void {
-		$this->assertEquals($expected, $report->getEndpoint());
-	}
+    /**
+     * @dataProvider generateReportsWithEndpoints
+     */
+    public function testGetEndpoint(MessageSentReport $report, string $expected): void
+    {
+        $this->assertEquals($expected, $report->getEndpoint());
+    }
 
-	public function generateReportsWithEndpoints(): array {
-		return [
-			[new MessageSentReport(new Request('POST', 'https://www.example.com')), 'https://www.example.com'],
-			[new MessageSentReport(new Request('POST', 'https://m.example.com')), 'https://m.example.com'],
-			[new MessageSentReport(new Request('POST', 'https://test.net')), 'https://test.net'],
-		];
-	}
+    public function generateReportsWithEndpoints(): array
+    {
+        return [
+            [new MessageSentReport(new Request('POST', 'https://www.example.com')), 'https://www.example.com'],
+            [new MessageSentReport(new Request('POST', 'https://m.example.com')), 'https://m.example.com'],
+            [new MessageSentReport(new Request('POST', 'https://test.net')), 'https://test.net'],
+        ];
+    }
 
-	/**
-	 * @dataProvider generateReportsWithRequests
-	 */
-	public function testGetRequest(MessageSentReport $report, Request $expected): void {
-		$this->assertEquals($expected, $report->getRequest());
-	}
+    /**
+     * @dataProvider generateReportsWithRequests
+     */
+    public function testGetRequest(MessageSentReport $report, Request $expected): void
+    {
+        $this->assertEquals($expected, $report->getRequest());
+    }
 
-	public function generateReportsWithRequests(): array {
-		$r1 = new Request('POST', 'https://www.example.com');
-		$r2 = new Request('PUT', 'https://m.example.com');
-		$r3 = new Request('GET', 'https://test.net');
+    public function generateReportsWithRequests(): array
+    {
+        $r1 = new Request('POST', 'https://www.example.com');
+        $r2 = new Request('PUT', 'https://m.example.com');
+        $r3 = new Request('GET', 'https://test.net');
 
-		return [
-			[new MessageSentReport($r1), $r1],
-			[new MessageSentReport($r2), $r2],
-			[new MessageSentReport($r3), $r3],
-		];
-	}
+        return [
+            [new MessageSentReport($r1), $r1],
+            [new MessageSentReport($r2), $r2],
+            [new MessageSentReport($r3), $r3],
+        ];
+    }
 
-	/**
-	 * @dataProvider generateReportsWithJson
-	 */
-	public function testJsonSerialize(MessageSentReport $report, string $json): void {
-		$this->assertJsonStringEqualsJsonString($json, json_encode($report, JSON_THROW_ON_ERROR));
-	}
+    /**
+     * @dataProvider generateReportsWithJson
+     */
+    public function testJsonSerialize(MessageSentReport $report, string $json): void
+    {
+        $this->assertJsonStringEqualsJsonString($json, json_encode($report, JSON_THROW_ON_ERROR));
+    }
 
-	public function generateReportsWithJson(): array {
-		$request1Body = json_encode(['title' => 'test', 'body' => 'blah', 'data' => []]);
-		$request1 = new Request('POST', 'https://www.example.com', [], $request1Body);
-		$response1 = new Response(200, [], 'test');
+    public function generateReportsWithJson(): array
+    {
+        $request1Body = json_encode(['title' => 'test', 'body' => 'blah', 'data' => []], JSON_THROW_ON_ERROR);
+        $request1 = new Request('POST', 'https://www.example.com', [], $request1Body);
+        $response1 = new Response(200, [], 'test');
 
-		$request2Body = '';
-		$request2 = new Request('POST', 'https://www.example.com', [], $request2Body);
-		$response2 = new Response(410, [], 'Faield to do somthing', '1.1', 'Gone');
+        $request2Body = '';
+        $request2 = new Request('POST', 'https://www.example.com', [], $request2Body);
+        $response2 = new Response(410, [], 'Failed to do something', '1.1', 'Gone');
 
-		return [
-			[
-				new MessageSentReport($request1, $response1),
-				json_encode([
-					'success'  => true,
-					'expired'  => false,
-					'reason'   => 'OK',
-					'endpoint' => (string) $request1->getUri(),
-					'payload'  => $request1Body,
-				], JSON_THROW_ON_ERROR)
-			],
-			[
-				new MessageSentReport($request2, $response2, false, 'Gone'),
-				json_encode([
-					'success'  => false,
-					'expired'  => true,
-					'reason'   => 'Gone',
-					'endpoint' => (string) $request2->getUri(),
-					'payload'  => $request2Body,
-				], JSON_THROW_ON_ERROR)
-			]
-		];
-	}
+        return [
+            [
+                new MessageSentReport($request1, $response1),
+                json_encode([
+                    'success'  => true,
+                    'expired'  => false,
+                    'reason'   => 'OK',
+                    'endpoint' => (string) $request1->getUri(),
+                    'payload'  => $request1Body,
+                ], JSON_THROW_ON_ERROR)
+            ],
+            [
+                new MessageSentReport($request2, $response2, false, 'Gone'),
+                json_encode([
+                    'success'  => false,
+                    'expired'  => true,
+                    'reason'   => 'Gone',
+                    'endpoint' => (string) $request2->getUri(),
+                    'payload'  => $request2Body,
+                ], JSON_THROW_ON_ERROR)
+            ]
+        ];
+    }
 
-	/**
-	 * @dataProvider generateReportsWithSuccess
-	 */
-	public function testIsSuccess(MessageSentReport $report, bool $expected): void {
-		$this->assertEquals($expected, $report->isSuccess());
-	}
+    /**
+     * @dataProvider generateReportsWithSuccess
+     */
+    public function testIsSuccess(MessageSentReport $report, bool $expected): void
+    {
+        $this->assertEquals($expected, $report->isSuccess());
+    }
 
-	public function generateReportsWithSuccess(): array {
+    public function generateReportsWithSuccess(): array
+    {
         $request = new Request('POST', 'https://example.com');
-		return [
-			[new MessageSentReport($request), true],
-			[new MessageSentReport($request, null, true), true],
-			[new MessageSentReport($request, null, false), false],
-		];
-	}
+        return [
+            [new MessageSentReport($request), true],
+            [new MessageSentReport($request, null, true), true],
+            [new MessageSentReport($request, null, false), false],
+        ];
+    }
 }
diff --git a/tests/PushServiceTest.php b/tests/PushServiceTest.php
index 510640f..f991652 100644
--- a/tests/PushServiceTest.php
+++ b/tests/PushServiceTest.php
@@ -11,22 +11,23 @@
  * file that was distributed with this source code.
  */
 
-use Minishlink\WebPush\WebPush;
+use Minishlink\WebPush\MessageSentReport;
 use Minishlink\WebPush\Subscription;
+use Minishlink\WebPush\WebPush;
 
 final class PushServiceTest extends PHPUnit\Framework\TestCase
 {
-    private static $timeout = 30;
-    private static $portNumber = 9012;
-    private static $testServiceUrl;
-    public static $vapidKeys = [
+    private static int    $timeout    = 30;
+    private static int    $portNumber = 9012;
+    private static string $testServiceUrl;
+    public static array   $vapidKeys  = [
         'subject' => 'http://test.com',
         'publicKey' => 'BA6jvk34k6YjElHQ6S0oZwmrsqHdCNajxcod6KJnI77Dagikfb--O_kYXcR2eflRz6l3PcI2r8fPCH3BElLQHDk',
         'privateKey' => '-3CdhFOqjzixgAbUSa0Zv9zi-dwDVmWO7672aBxSFPQ',
     ];
 
     /** @var WebPush WebPush with correct api keys */
-    private $webPush;
+    private WebPush $webPush;
 
     /**
      * {@inheritdoc}
@@ -36,7 +37,7 @@ public static function setUpBeforeClass(): void
         self::$testServiceUrl = 'http://localhost:'.self::$portNumber;
     }
 
-    public function browserProvider()
+    public function browserProvider(): array
     {
         return [
             ['firefox', ['VAPID' => self::$vapidKeys]],
@@ -49,7 +50,7 @@ public function browserProvider()
     /**
      * Selenium tests are flakey so add retries.
      */
-    public function retryTest($retryCount, $test)
+    public function retryTest($retryCount, $test): void
     {
         // just like above without checking the annotation
         for ($i = 0; $i < $retryCount; $i++) {
@@ -70,12 +71,12 @@ public function retryTest($retryCount, $test)
      * @dataProvider browserProvider
      * Run integration tests with browsers
      */
-    public function testBrowsers($browserId, $options)
+    public function testBrowsers($browserId, $options): void
     {
         $this->retryTest(2, $this->createClosureTest($browserId, $options));
     }
 
-    protected function createClosureTest($browserId, $options)
+    protected function createClosureTest($browserId, $options): callable
     {
         return function () use ($browserId, $options) {
             $this->webPush = new WebPush($options);
@@ -115,19 +116,19 @@ protected function createClosureTest($browserId, $options)
 
             foreach ($supportedContentEncodings as $contentEncoding) {
                 if (!in_array($contentEncoding, ['aesgcm', 'aes128gcm'])) {
-                    $this->expectException(\ErrorException::class);
+                    $this->expectException(ErrorException::class);
                     $this->expectExceptionMessage('This content encoding ('.$contentEncoding.') is not supported.');
                     $this->markTestIncomplete('Unsupported content encoding: '.$contentEncoding);
                 }
 
                 $subscription = new Subscription($endpoint, $p256dh, $auth, $contentEncoding);
                 $report = $this->webPush->sendOneNotification($subscription, $payload);
-                $this->assertInstanceOf(\Minishlink\WebPush\MessageSentReport::class, $report);
+                $this->assertInstanceOf(MessageSentReport::class, $report);
                 $this->assertTrue($report->isSuccess());
 
                 $dataString = json_encode([
-                    'clientHash' => $clientHash,
-                ]);
+                                              'clientHash' => $clientHash,
+                                          ], JSON_THROW_ON_ERROR);
 
                 $getNotificationCurl = curl_init(self::$testServiceUrl.'/get-notifications');
                 curl_setopt_array($getNotificationCurl, [
@@ -144,7 +145,7 @@ protected function createClosureTest($browserId, $options)
                 $parsedResp = $this->getResponse($getNotificationCurl);
 
                 if (!property_exists($parsedResp->{'data'}, 'messages')) {
-                    throw new Exception('web-push-testing error, no messages: '.json_encode($parsedResp));
+                    throw new RuntimeException('web-push-testing error, no messages: '.json_encode($parsedResp, JSON_THROW_ON_ERROR));
                 }
 
                 $messages = $parsedResp->{'data'}->{'messages'};
@@ -161,13 +162,13 @@ private function getResponse($ch)
         if (!$resp) {
             $error = 'Curl error: n'.curl_errno($ch).' - '.curl_error($ch);
             curl_close($ch);
-            throw new Exception($error);
+            throw new RuntimeException($error);
         }
 
         $parsedResp = json_decode($resp, null, 512, JSON_THROW_ON_ERROR);
 
         if (!property_exists($parsedResp, 'data')) {
-            throw new Exception('web-push-testing-service error: '.$resp);
+            throw new RuntimeException('web-push-testing-service error: '.$resp);
         }
 
         // Close request to clear up some resources
diff --git a/tests/SubscriptionTest.php b/tests/SubscriptionTest.php
index bbe5353..3f64109 100644
--- a/tests/SubscriptionTest.php
+++ b/tests/SubscriptionTest.php
@@ -4,7 +4,7 @@
 
 class SubscriptionTest extends PHPUnit\Framework\TestCase
 {
-    public function testCreateMinimal()
+    public function testCreateMinimal(): void
     {
         $subscriptionArray = array(
             "endpoint" => "http://toto.com"
@@ -16,7 +16,7 @@ public function testCreateMinimal()
         $this->assertEquals(null, $subscription->getContentEncoding());
     }
 
-    public function testConstructMinimal()
+    public function testConstructMinimal(): void
     {
         $subscription = new Subscription("http://toto.com");
         $this->assertEquals("http://toto.com", $subscription->getEndpoint());
@@ -25,7 +25,7 @@ public function testConstructMinimal()
         $this->assertEquals(null, $subscription->getContentEncoding());
     }
 
-    public function testCreatePartial()
+    public function testCreatePartial(): void
     {
         $subscriptionArray = array(
             "endpoint" => "http://toto.com",
@@ -39,7 +39,7 @@ public function testCreatePartial()
         $this->assertEquals("aesgcm", $subscription->getContentEncoding());
     }
 
-    public function testConstructPartial()
+    public function testConstructPartial(): void
     {
         $subscription = new Subscription("http://toto.com", "publicKey", "authToken");
         $this->assertEquals("http://toto.com", $subscription->getEndpoint());
@@ -48,7 +48,7 @@ public function testConstructPartial()
         $this->assertEquals("aesgcm", $subscription->getContentEncoding());
     }
 
-    public function testCreateFull()
+    public function testCreateFull(): void
     {
         $subscriptionArray = array(
             "endpoint" => "http://toto.com",
@@ -63,7 +63,7 @@ public function testCreateFull()
         $this->assertEquals("aes128gcm", $subscription->getContentEncoding());
     }
 
-    public function testConstructFull()
+    public function testConstructFull(): void
     {
         $subscription = new Subscription("http://toto.com", "publicKey", "authToken", "aes128gcm");
         $this->assertEquals("http://toto.com", $subscription->getEndpoint());
@@ -72,7 +72,7 @@ public function testConstructFull()
         $this->assertEquals("aes128gcm", $subscription->getContentEncoding());
     }
 
-    public function testCreatePartialWithNewStructure()
+    public function testCreatePartialWithNewStructure(): void
     {
         $subscription = Subscription::create([
             "endpoint" => "http://toto.com",
@@ -86,7 +86,7 @@ public function testCreatePartialWithNewStructure()
         $this->assertEquals("authToken", $subscription->getAuthToken());
     }
 
-    public function testCreatePartialWithNewStructureAndContentEncoding()
+    public function testCreatePartialWithNewStructureAndContentEncoding(): void
     {
         $subscription = Subscription::create([
             "endpoint" => "http://toto.com",
diff --git a/tests/UtilsTest.php b/tests/UtilsTest.php
index 462241f..68e6ede 100644
--- a/tests/UtilsTest.php
+++ b/tests/UtilsTest.php
@@ -1,13 +1,12 @@
 <?php
 
-use Jose\Component\Core\Util\Ecc\NistCurve;
 use Jose\Component\KeyManagement\JWKFactory;
 use Minishlink\WebPush\Utils;
 use PHPUnit\Framework\TestCase;
 
 final class UtilsTest extends TestCase
 {
-    public function testSerializePublicKey()
+    public function testSerializePublicKey(): void
     {
         $jwk = JWKFactory::createECKey('P-256');
         $serializedPublicKey = Utils::serializePublicKeyFromJWK($jwk);
diff --git a/tests/VAPIDTest.php b/tests/VAPIDTest.php
index 1958b0d..40b4275 100644
--- a/tests/VAPIDTest.php
+++ b/tests/VAPIDTest.php
@@ -16,7 +16,7 @@
 
 final class VAPIDTest extends PHPUnit\Framework\TestCase
 {
-    public function vapidProvider() : array
+    public function vapidProvider(): array
     {
         return [
             [
@@ -50,7 +50,7 @@ public function vapidProvider() : array
      *
      * @throws ErrorException
      */
-    public function testGetVapidHeaders(string $audience, array $vapid, string $contentEncoding, int $expiration, string $expectedAuthorization, ?string $expectedCryptoKey)
+    public function testGetVapidHeaders(string $audience, array $vapid, string $contentEncoding, int $expiration, string $expectedAuthorization, ?string $expectedCryptoKey): void
     {
         $vapid = VAPID::validate($vapid);
         $headers = VAPID::getVapidHeaders(
@@ -75,16 +75,17 @@ public function testGetVapidHeaders(string $audience, array $vapid, string $cont
     }
 
     /**
-     * @return array|string
+     * @param string $auth
+     * @return array
      */
-    private function explodeAuthorization(string $auth)
+    private function explodeAuthorization(string $auth): array
     {
         $auth = explode('.', $auth);
         array_pop($auth); // delete the signature which changes each time
         return $auth;
     }
 
-    public function testCreateVapidKeys()
+    public function testCreateVapidKeys(): void
     {
         $keys = VAPID::createVapidKeys();
         $this->assertArrayHasKey('publicKey', $keys);
diff --git a/tests/WebPushTest.php b/tests/WebPushTest.php
index c936dfe..d6f756c 100644
--- a/tests/WebPushTest.php
+++ b/tests/WebPushTest.php
@@ -11,19 +11,19 @@
  * file that was distributed with this source code.
  */
 
-use Minishlink\WebPush\WebPush;
 use Minishlink\WebPush\Subscription;
 use Minishlink\WebPush\SubscriptionInterface;
+use Minishlink\WebPush\WebPush;
 
 final class WebPushTest extends PHPUnit\Framework\TestCase
 {
-    private static $endpoints;
-    private static $keys;
-    private static $tokens;
-    private static $vapidKeys;
+    private static array $endpoints;
+    private static array $keys;
+    private static array $tokens;
+    private static array $vapidKeys;
 
     /** @var WebPush WebPush with correct api keys */
-    private $webPush;
+    private WebPush $webPush;
 
     /**
      * {@inheritdoc}
@@ -48,7 +48,7 @@ public static function setUpBeforeClass(): void
         ];
 
         if (getenv('CI')) {
-            self::setCiEnvironment();;
+            self::setCiEnvironment();
         }
     }
 
@@ -108,7 +108,7 @@ private static function setCiEnvironment(): void
         if (!$response) {
             $error = 'Curl error: n'.curl_errno($getSubscriptionCurl).' - '.curl_error($getSubscriptionCurl);
             curl_close($getSubscriptionCurl);
-            throw new Exception($error);
+            throw new RuntimeException($error);
         }
 
         $parsedResp = json_decode($response, null, 512, JSON_THROW_ON_ERROR);
@@ -137,10 +137,10 @@ public function notificationProvider(): array
      * @dataProvider notificationProvider
      *
      * @param SubscriptionInterface $subscription
-     * @param string $payload
+     * @param string                $payload
      * @throws ErrorException
      */
-    public function testSendOneNotification($subscription, $payload)
+    public function testSendOneNotification(SubscriptionInterface $subscription, string $payload): void
     {
         $report = $this->webPush->sendOneNotification($subscription, $payload);
         $this->assertTrue($report->isSuccess());
@@ -149,7 +149,7 @@ public function testSendOneNotification($subscription, $payload)
     /**
      * @throws ErrorException
      */
-    public function testSendNotificationBatch()
+    public function testSendNotificationBatch(): void
     {
         $batchSize = 10;
         $total = 50;
@@ -171,9 +171,9 @@ public function testSendNotificationBatch()
     /**
      * @throws ErrorException
      */
-    public function testSendOneNotificationWithTooBigPayload()
+    public function testSendOneNotificationWithTooBigPayload(): void
     {
-        $this->expectException(\ErrorException::class);
+        $this->expectException(ErrorException::class);
         $this->expectExceptionMessage('Size of payload must not be greater than 4078 octets.');
 
         $subscription = new Subscription(self::$endpoints['standard'], self::$keys['standard']);
@@ -184,57 +184,61 @@ public function testSendOneNotificationWithTooBigPayload()
     }
 
     /**
-     * @throws ErrorException
+     * @throws \ErrorException
+     * @throws \JsonException
      */
-    public function testFlush() {
-	    $subscription = new Subscription(self::$endpoints['standard']);
+    public function testFlush(): void
+    {
+        $subscription = new Subscription(self::$endpoints['standard']);
 
-	    $report = $this->webPush->sendOneNotification($subscription);
-	    $this->assertFalse($report->isSuccess()); // it doesn't have VAPID
+        $report = $this->webPush->sendOneNotification($subscription);
+        $this->assertFalse($report->isSuccess()); // it doesn't have VAPID
 
-	    // queue has been reset
-	    $this->assertEmpty(iterator_to_array($this->webPush->flush()));
+        // queue has been reset
+        $this->assertEmpty(iterator_to_array($this->webPush->flush()));
 
         $report = $this->webPush->sendOneNotification($subscription);
         $this->assertFalse($report->isSuccess());  // it doesn't have VAPID
 
-	    $nonExistantSubscription = Subscription::create([
-		    'endpoint'        => 'https://fcm.googleapis.com/fcm/send/fCd2-8nXJhU:APA91bGi2uaqFXGft4qdolwyRUcUPCL1XV_jWy1tpCRqnu4sk7ojUpC5gnq1PTncbCdMq9RCVQIIFIU9BjzScvjrDqpsI7J-K_3xYW8xo1xSNCfge1RvJ6Xs8RGL_Sw7JtbCyG1_EVgWDc22on1r_jozD8vsFbB0Fg',
-		    'publicKey'       => 'BME-1ZSAv2AyGjENQTzrXDj6vSnhAIdKso4n3NDY0lsd1DUgEzBw7ARMKjrYAm7JmJBPsilV5CWNH0mVPyJEt0Q',
-		    'authToken'       => 'hUIGbmiypj9_EQea8AnCKA',
-		    'contentEncoding' => 'aes128gcm',
-	    ]);
-
-	    // test multiple requests
-	    $this->webPush->queueNotification($nonExistantSubscription, json_encode(['test' => 1]));
-	    $this->webPush->queueNotification($nonExistantSubscription, json_encode(['test' => 2]));
-	    $this->webPush->queueNotification($nonExistantSubscription, json_encode(['test' => 3]));
-
-	    /** @var \Minishlink\WebPush\MessageSentReport $report */
-	    foreach ($this->webPush->flush() as $report) {
-	    	$this->assertFalse($report->isSuccess());
-	    	$this->assertTrue($report->isSubscriptionExpired());
-	    	$this->assertEquals(410, $report->getResponse()->getStatusCode());
-	    	$this->assertNotEmpty($report->getReason());
-	    	$this->assertNotFalse(filter_var($report->getEndpoint(), FILTER_VALIDATE_URL));
-	    }
+        $nonExistentSubscription = Subscription::create([
+            'endpoint'        => 'https://fcm.googleapis.com/fcm/send/fCd2-8nXJhU:APA91bGi2uaqFXGft4qdolwyRUcUPCL1XV_jWy1tpCRqnu4sk7ojUpC5gnq1PTncbCdMq9RCVQIIFIU9BjzScvjrDqpsI7J-K_3xYW8xo1xSNCfge1RvJ6Xs8RGL_Sw7JtbCyG1_EVgWDc22on1r_jozD8vsFbB0Fg',
+            'publicKey'       => 'BME-1ZSAv2AyGjENQTzrXDj6vSnhAIdKso4n3NDY0lsd1DUgEzBw7ARMKjrYAm7JmJBPsilV5CWNH0mVPyJEt0Q',
+            'authToken'       => 'hUIGbmiypj9_EQea8AnCKA',
+            'contentEncoding' => 'aes128gcm',
+        ]);
+
+        // test multiple requests
+        $this->webPush->queueNotification($nonExistentSubscription, json_encode(['test' => 1], JSON_THROW_ON_ERROR));
+        $this->webPush->queueNotification($nonExistentSubscription, json_encode(['test' => 2], JSON_THROW_ON_ERROR));
+        $this->webPush->queueNotification($nonExistentSubscription, json_encode(['test' => 3], JSON_THROW_ON_ERROR));
+
+        /** @var \Minishlink\WebPush\MessageSentReport $report */
+        foreach ($this->webPush->flush() as $report) {
+            $this->assertFalse($report->isSuccess());
+            $this->assertTrue($report->isSubscriptionExpired());
+            $this->assertEquals(410, $report->getResponse()->getStatusCode());
+            $this->assertNotEmpty($report->getReason());
+            $this->assertNotFalse(filter_var($report->getEndpoint(), FILTER_VALIDATE_URL));
+        }
     }
 
-	public function testFlushEmpty(): void {
+    public function testFlushEmpty(): void
+    {
         $this->assertEmpty(iterator_to_array($this->webPush->flush(300)));
     }
 
-	/**
-	 * @throws ErrorException
-	 */
-	public function testCount(): void {
-		$subscription = new Subscription(self::$endpoints['standard']);
+    /**
+     * @throws ErrorException
+     */
+    public function testCount(): void
+    {
+        $subscription = new Subscription(self::$endpoints['standard']);
 
-		$this->webPush->queueNotification($subscription);
-		$this->webPush->queueNotification($subscription);
-		$this->webPush->queueNotification($subscription);
-		$this->webPush->queueNotification($subscription);
+        $this->webPush->queueNotification($subscription);
+        $this->webPush->queueNotification($subscription);
+        $this->webPush->queueNotification($subscription);
+        $this->webPush->queueNotification($subscription);
 
-		$this->assertEquals(4, $this->webPush->countPendingNotifications());
+        $this->assertEquals(4, $this->webPush->countPendingNotifications());
     }
 }