diff --git a/.gitignore b/.gitignore
index 5049f84..ce45a9c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 /vendor
 /.idea
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diff --git a/composer.json b/composer.json
index f837d68..0148c37 100644
--- a/composer.json
+++ b/composer.json
@@ -16,15 +16,15 @@
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+        "harmonyio/php-codesniffer-ruleset": "dev-master",
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+        "maglnet/composer-require-checker": "^2.0.0",
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diff --git a/composer.lock b/composer.lock
index d84dfe6..ee1578c 100644
--- a/composer.lock
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@@ -249,33 +249,31 @@
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                 "php": ">=7.0"
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@@ -323,20 +321,20 @@
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@@ -389,20 +387,20 @@
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@@ -452,7 +450,7 @@
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@@ -507,16 +505,16 @@
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@@ -862,32 +860,32 @@
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@@ -961,27 +959,29 @@
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-                "squizlabs/php_codesniffer": "^3.0.2"
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@@ -1006,30 +1006,30 @@
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-            "homepage": "https://github.com/doctrine/instantiator",
+            "homepage": "https://www.doctrine-project.org/projects/instantiator.html",
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-            "time": "2017-07-22T11:58:36+00:00"
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-                "slevomat/coding-standard": "^4.8.6",
-                "squizlabs/php_codesniffer": "^3.4.0"
+                "harmonyio/php-codesniffer-ruleset": "dev-master",
+                "maglnet/composer-require-checker": "^2.0.0",
+                "slevomat/coding-standard": "^5.0.4",
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@@ -1087,33 +1087,34 @@
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-                "php": "~7.1",
-                "symfony/console": "~3.0|~4.0",
-                "webmozart/glob": "^4.1@dev"
+                "nikic/php-parser": "^4.0",
+                "php": "^7.1",
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-                "phpunit/phpunit": "~6.0"
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@@ -1121,7 +1122,7 @@
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@@ -1146,7 +1147,7 @@
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@@ -1156,20 +1157,20 @@
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-            "time": "2018-09-03T09:27:25+00:00"
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@@ -1204,20 +1205,20 @@
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@@ -1233,7 +1234,7 @@
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@@ -1255,7 +1256,7 @@
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@@ -1574,42 +1575,89 @@
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+            "version": "0.3.3",
+            "source": {
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+                "url": "https://github.com/phpstan/phpdoc-parser.git",
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             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/theseer/tokenizer/zipball/cb2f008f3f05af2893a87208fe6a6c4985483f8b",
-                "reference": "cb2f008f3f05af2893a87208fe6a6c4985483f8b",
+                "url": "https://api.github.com/repos/theseer/tokenizer/zipball/1c42705be2b6c1de5904f8afacef5895cab44bf8",
+                "reference": "1c42705be2b6c1de5904f8afacef5895cab44bf8",
                 "shasum": ""
             },
             "require": {
@@ -2855,7 +2911,7 @@
                 }
             ],
             "description": "A small library for converting tokenized PHP source code into XML and potentially other formats",
-            "time": "2017-04-07T12:08:54+00:00"
+            "time": "2019-04-04T09:56:43+00:00"
         },
         {
             "name": "webmozart/assert",
@@ -3004,7 +3060,11 @@
     ],
     "aliases": [],
     "minimum-stability": "dev",
-    "stability-flags": [],
+    "stability-flags": {
+        "harmonyio/cache": 20,
+        "harmonyio/php-codesniffer-ruleset": 20,
+        "harmonyio/phpunit-extension": 20
+    },
     "prefer-stable": true,
     "prefer-lowest": false,
     "platform": {
diff --git a/src/Client/ArtaxClient.php b/src/Client/ArtaxClient.php
index 7b78d03..9e8552a 100644
--- a/src/Client/ArtaxClient.php
+++ b/src/Client/ArtaxClient.php
@@ -49,7 +49,7 @@ private function makeCachingRequest(CachingRequest $request): Promise
                 yield $this->cache->store(new Item(
                     $request->getCachingKey(),
                     serialize($response),
-                    $request->getTtl()
+                    $request->getTtl(),
                 ));
             }
 
diff --git a/src/Message/Response.php b/src/Message/Response.php
index 16ff915..489947b 100644
--- a/src/Message/Response.php
+++ b/src/Message/Response.php
@@ -17,7 +17,7 @@ class Response implements CacheableResponse
     /** @var string */
     private $textualStatusCode;
 
-    /** @var array<string, string[]> */
+    /** @var array<string, array<string>> */
     private $headers = [];
 
     /** @var string */
@@ -62,7 +62,7 @@ public function getHeader(string $key): ?string
     }
 
     /**
-     * @return string[]
+     * @return array<string>
      */
     public function getHeaderArray(string $key): array
     {
diff --git a/tests/Unit/Client/ArtaxClientTest.php b/tests/Unit/Client/ArtaxClientTest.php
index 4a31b1a..732334b 100644
--- a/tests/Unit/Client/ArtaxClientTest.php
+++ b/tests/Unit/Client/ArtaxClientTest.php
@@ -27,8 +27,7 @@ class ArtaxClientTest extends TestCase
     /** @var MockObject|Cache */
     private $cache;
 
-    // phpcs:ignore SlevomatCodingStandard.TypeHints.TypeHintDeclaration.MissingReturnTypeHint
-    public function setUp()
+    public function setUp(): void
     {
         $this->artaxBaseClient = $this->createMock(ArtaxBaseClient::class);
         $this->cache           = $this->createMock(Cache::class);
diff --git a/tests/Unit/Exception/InvalidBodyTest.php b/tests/Unit/Exception/InvalidBodyTest.php
index d4252ce..daceb44 100644
--- a/tests/Unit/Exception/InvalidBodyTest.php
+++ b/tests/Unit/Exception/InvalidBodyTest.php
@@ -19,7 +19,7 @@ public function testMessageWhenBodyTypeIsAnObject(): void
     {
         $this->expectException(InvalidBody::class);
         $this->expectExceptionMessage(
-            'Expected body to be of type string|Amp\Artax\RequestBody, but got DateTimeImmutable.'
+            'Expected body to be of type string|Amp\Artax\RequestBody, but got DateTimeImmutable.',
         );
 
         throw new InvalidBody(new \DateTimeImmutable());
diff --git a/tests/Unit/Message/CachingRequestTest.php b/tests/Unit/Message/CachingRequestTest.php
index 87e3d63..b3b2aa1 100644
--- a/tests/Unit/Message/CachingRequestTest.php
+++ b/tests/Unit/Message/CachingRequestTest.php
@@ -14,7 +14,7 @@ public function testImplementsCachingInterface(): void
     {
         $this->assertInstanceOf(
             CacheableRequest::class,
-            (new CachingRequest('TestKey', new Ttl(10), 'https://example.com'))
+            (new CachingRequest('TestKey', new Ttl(10), 'https://example.com')),
         );
     }
 
@@ -29,7 +29,7 @@ public function testGetTtl(): void
     {
         $this->assertSame(
             10,
-            (new CachingRequest('TestKey', new Ttl(10), 'https://example.com'))->getTtl()->getTtlInSeconds()
+            (new CachingRequest('TestKey', new Ttl(10), 'https://example.com'))->getTtl()->getTtlInSeconds(),
         );
     }
 }
diff --git a/tests/Unit/Message/ResponseTest.php b/tests/Unit/Message/ResponseTest.php
index aa685ca..94aa6ad 100644
--- a/tests/Unit/Message/ResponseTest.php
+++ b/tests/Unit/Message/ResponseTest.php
@@ -106,7 +106,7 @@ public function testSerialize(): void
     {
         $this->assertSame(
             require TEST_FIXTURE_DIR . '/Message/serialized-response.php',
-            serialize($this->response)
+            serialize($this->response),
         );
     }