diff --git a/Tests/IntegrationTest.php b/Tests/IntegrationTest.php
index 155e757..f3be195 100644
--- a/Tests/IntegrationTest.php
+++ b/Tests/IntegrationTest.php
@@ -21,25 +21,25 @@
  */
 class IntegrationTest extends ProviderIntegrationTest
 {
-    protected $skippedTests = [
+    protected array $skippedTests = [
         'testReverseQueryWithNoResults' => 'Null island exists. ',
     ];
 
-    protected $testIpv4 = false;
+    protected bool $testIpv4 = false;
 
-    protected $testIpv6 = false;
+    protected bool $testIpv6 = false;
 
     protected function createProvider(ClientInterface $httpClient)
     {
         return new TomTom($httpClient, $this->getApiKey());
     }
 
-    protected function getCacheDir()
+    protected function getCacheDir(): string
     {
         return __DIR__.'/.cached_responses';
     }
 
-    protected function getApiKey()
+    protected function getApiKey(): string
     {
         return $_SERVER['TOMTOM_MAP_KEY'];
     }