diff --git a/src/ChatSession.php b/src/ChatSession.php
index 013b9c7..34f3ae6 100644
--- a/src/ChatSession.php
+++ b/src/ChatSession.php
@@ -37,7 +37,7 @@ public function sendMessage(PartInterface ...$parts): GenerateContentResponse
             ->withGenerationConfig($config)
             ->generateContentWithContents($this->history);
 
-        if(!empty($response->candidates)) {
+        if (!empty($response->candidates)) {
             $parts = $response->candidates[0]->content->parts;
             $this->history[] = new Content($parts, Role::Model);
         }
@@ -58,7 +58,7 @@ public function sendMessageStream(
 
         $parts = [];
         $partsCollectorCallback = function (GenerateContentResponse $response) use ($callback, &$parts) {
-            if(!empty($response->candidates)) {
+            if (!empty($response->candidates)) {
                 array_push($parts, ...$response->parts());
             }
 
diff --git a/tests/Unit/ClientTest.php b/tests/Unit/ClientTest.php
index 0bd11c6..0e8f25e 100644
--- a/tests/Unit/ClientTest.php
+++ b/tests/Unit/ClientTest.php
@@ -23,7 +23,7 @@
 
 class ClientTest extends TestCase
 {
-    public function testConstructor()
+    public function testConstructor(): void
     {
         $client = new Client(
             'test-api-key',
@@ -32,7 +32,7 @@ public function testConstructor()
         self::assertInstanceOf(Client::class, $client);
     }
 
-    public function testWithBaseUrl()
+    public function testWithBaseUrl(): void
     {
         $client = new Client(
             'test-api-key',
@@ -42,7 +42,7 @@ public function testWithBaseUrl()
         self::assertInstanceOf(Client::class, $client);
     }
 
-    public function testGeminiPro()
+    public function testGeminiPro(): void
     {
         $client = new Client(
             'test-api-key',
@@ -53,7 +53,7 @@ public function testGeminiPro()
         self::assertEquals(ModelName::GEMINI_PRO, $model->modelName);
     }
 
-    public function testGeminiProWithEnum()
+    public function testGeminiProWithEnum(): void
     {
         $client = new Client(
             'test-api-key',
@@ -75,7 +75,7 @@ public function testGenerativeModel()
         self::assertEquals(ModelName::EMBEDDING_001, $model->modelName);
     }
 
-    public function testGenerateContent()
+    public function testGenerateContent(): void
     {
         $httpRequest = new Request(
             'POST',
@@ -152,7 +152,7 @@ public function testGenerateContent()
         self::assertEquals('This is the Gemini Pro response', $response->text());
     }
 
-    public function testEmbedContent()
+    public function testEmbedContent(): void
     {
         $httpRequest = new Request(
             'POST',
@@ -207,7 +207,7 @@ public function testEmbedContent()
         self::assertEquals([0.041395925, -0.017692696], $response->embedding->values);
     }
 
-    public function testCountTokens()
+    public function testCountTokens(): void
     {
         $httpRequest = new Request(
             'POST',
@@ -257,7 +257,7 @@ public function testCountTokens()
         self::assertEquals(10, $response->totalTokens);
     }
 
-    public function testListModels()
+    public function testListModels(): void
     {
         $httpRequest = new Request(
             'GET',