diff --git a/src/Client.php b/src/Client.php
index c4eaa10..2490d1e 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -5,6 +5,7 @@
 use GuzzleHttp\Exception\GuzzleException;
 use Luft\ApiClient\ApiClient;
 use Luft\HttpClient\HttpClient;
+use Luft\HttpClient\HttpClientInterface;
 use Luft\Models\Installation\Installation;
 use Luft\Models\Measurement\Measurement;
 use Symfony\Component\Serializer\Exception\ExceptionInterface;
@@ -36,9 +37,14 @@ class Client
      */
     private $headers;
 
-    public function __construct(string $apiKey)
+    /**
+     * Client constructor.
+     * @param string $apiKey
+     * @param HttpClientInterface|null $httpClient
+     */
+    public function __construct(string $apiKey, HttpClientInterface $httpClient = null)
     {
-        $httpClient = new HttpClient();
+        $httpClient = $httpClient ?? new HttpClient();
         $serializer = Serializer::getInstance();
         $this->apiKey = $apiKey;
         $this->client = new ApiClient($httpClient, $serializer);
@@ -90,7 +96,7 @@ public function getInstallationsNearest(
      */
     public function getInstallation(int $installationId): Installation
     {
-        $this->client->getInstallation($installationId);
+        return $this->client->getInstallation($installationId);
     }
 
     /**
@@ -107,7 +113,7 @@ public function getMeasurementsForInstallation(
         ?string $indexType = null
     ): Measurement
     {
-        $this->client->getMeasurementsForInstallation($installationId, $includeWind, $indexType);
+        return $this->client->getMeasurementsForInstallation($installationId, $includeWind, $indexType);
     }
 
     /**
@@ -126,7 +132,7 @@ public function getMeasurementsNearest(
         ?string $indexType = null
     ): Measurement
     {
-        $this->client->getMeasurementsNearest($lat, $lng, $maxDistanceKM, $indexType);
+        return $this->client->getMeasurementsNearest($lat, $lng, $maxDistanceKM, $indexType);
     }
 
     /**
@@ -142,7 +148,7 @@ public function getMeasurementsPoint(
         ?string $indexType = null
     ): Measurement
     {
-        $this->client->getMeasurementsPoint($lat, $lng, $indexType);
+        return $this->client->getMeasurementsPoint($lat, $lng, $indexType);
     }
 
     /**
diff --git a/src/HttpClient/HttpClient.php b/src/HttpClient/HttpClient.php
index 0060da5..929e9e1 100644
--- a/src/HttpClient/HttpClient.php
+++ b/src/HttpClient/HttpClient.php
@@ -16,7 +16,10 @@ class HttpClient implements HttpClientInterface
      */
     private $client;
 
-    public function __construct($handler = null)
+    /**
+     * @param callable $handler
+     */
+    public function __construct(callable $handler = null)
     {
         $config = [
             'base_uri' => self::BASE_URI
diff --git a/tests/unit/ClientTest.php b/tests/unit/ClientTest.php
index 50421c8..2bc5497 100644
--- a/tests/unit/ClientTest.php
+++ b/tests/unit/ClientTest.php
@@ -4,6 +4,7 @@
 use GuzzleHttp\Handler\MockHandler;
 use GuzzleHttp\Psr7\Response;
 use Luft\ApiClient\ApiClient;
+use Luft\Client;
 use Luft\HttpClient\HttpClient;
 use Luft\Models\Installation\Address;
 use Luft\Models\Installation\Coordinates;
@@ -12,7 +13,6 @@
 use Luft\Models\Measurement\Measurement;
 use Luft\Models\Meta\Level;
 use Luft\Models\Meta\Type;
-use Luft\Serializer;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Serializer\Exception\ExceptionInterface;
 
@@ -32,15 +32,14 @@ class ClientTest extends TestCase
     protected function setUp(): void
     {
         $this->mockHandler = new MockHandler();
-        $this->client = new ApiClient(new HttpClient($this->mockHandler), Serializer::getInstance());
+        $this->client = new Client('randomKey', new HttpClient($this->mockHandler));
     }
 
     /**
-     * @test
      * @throws GuzzleException
      * @throws ExceptionInterface
      */
-    public function getMetaIndexes(): void
+    public function testGetMetaIndexes(): void
     {
         $this->mockHandler->append(new Response(200, [], file_get_contents(__DIR__ . '/data/meta.indexes.json')));
 
@@ -60,11 +59,10 @@ public function getMetaIndexes(): void
     }
 
     /**
-     * @test
      * @throws GuzzleException
      * @throws ExceptionInterface
      */
-    public function getInstallationsNearest(): void
+    public function testGetInstallationsNearest(): void
     {
         $this->mockHandler->append(new Response(200, [],
             file_get_contents(__DIR__ . '/data/installations.nearest.json')));
@@ -89,11 +87,10 @@ public function getInstallationsNearest(): void
     }
 
     /**
-     * @test
      * @throws GuzzleException
      * @throws ExceptionInterface
      */
-    public function getInstallationId(): void
+    public function testGetInstallationId(): void
     {
         $this->mockHandler->append(new Response(200, [],
             file_get_contents(__DIR__ . '/data/installations.id.json')));
@@ -104,11 +101,10 @@ public function getInstallationId(): void
     }
 
     /**
-     * @test
      * @throws ExceptionInterface
      * @throws GuzzleException
      */
-    public function getMeasurementsForInstallation(): void
+    public function testGetMeasurementsForInstallation(): void
     {
         $this->mockHandler->append(new Response(200, [],
             file_get_contents(__DIR__ . '/data/measurements.installation.json')));
@@ -127,11 +123,10 @@ public function getMeasurementsForInstallation(): void
     }
 
     /**
-     * @test
      * @throws ExceptionInterface
      * @throws GuzzleException
      */
-    public function getMeasurementsNearest(): void
+    public function testGetMeasurementsNearest(): void
     {
         $this->mockHandler->append(new Response(200, [],
             file_get_contents(__DIR__ . '/data/measurements.nearest.json')));
@@ -144,12 +139,12 @@ public function getMeasurementsNearest(): void
     }
 
     /**
-     * @test
+     * @throws ExceptionInterface
      */
-    public function getMeasurementsPoint(): void
+    public function testGetMeasurementsPoint(): void
     {
         $this->mockHandler->append(new Response(200, [],
-            file_get_contents(__DIR__ . '/data/measurements.nearest.json')));
+            file_get_contents(__DIR__ . '/data/measurements.point.json')));
 
         $result = $this->client->getMeasurementsPoint(50.062006, 19.940984, 'AIRLY_CAQI');
         $this->assertInstanceOf(Measurement::class, $result);