diff --git a/src/HttpBaseTest.php b/src/HttpBaseTest.php
index 79fb058..44a7f7d 100644
--- a/src/HttpBaseTest.php
+++ b/src/HttpBaseTest.php
@@ -10,6 +10,8 @@
 
 abstract class HttpBaseTest extends TestCase
 {
+    use PhpUnitBackwardCompatibleTrait;
+
     /**
      * @var string
      */
@@ -221,7 +223,7 @@ protected function assertResponse(ResponseInterface $response, array $options =
         if (null === $options['body']) {
             $this->assertEmpty($response->getBody()->__toString());
         } else {
-            $this->assertContains($options['body'], $response->getBody()->__toString());
+            $this->assertStringContainsString($options['body'], $response->getBody()->__toString());
         }
     }
 
diff --git a/src/HttpClientTest.php b/src/HttpClientTest.php
index 5c82aa6..aaaf7a4 100644
--- a/src/HttpClientTest.php
+++ b/src/HttpClientTest.php
@@ -3,6 +3,7 @@
 namespace Http\Client\Tests;
 
 use Psr\Http\Client\ClientInterface;
+use Psr\Http\Client\NetworkExceptionInterface;
 
 /**
  * @author GeLo <geloen.eric@gmail.com>
@@ -92,8 +93,7 @@ public function testSendRequestWithOutcome($uriAndOutcome, $protocolVersion, arr
     }
 
     /**
-     * @expectedException \Psr\Http\Client\NetworkExceptionInterface
-     * @group             integration
+     * @group integration
      */
     public function testSendWithInvalidUri()
     {
@@ -103,6 +103,7 @@ public function testSendWithInvalidUri()
             $this->defaultHeaders
         );
 
+        $this->expectException(NetworkExceptionInterface::class);
         $this->httpAdapter->sendRequest($request);
     }
 }
diff --git a/src/HttpFeatureTest.php b/src/HttpFeatureTest.php
index 08f7ced..fd4836f 100644
--- a/src/HttpFeatureTest.php
+++ b/src/HttpFeatureTest.php
@@ -9,6 +9,8 @@
 
 abstract class HttpFeatureTest extends TestCase
 {
+    use PhpUnitBackwardCompatibleTrait;
+
     /**
      * @var MessageFactory
      */
@@ -141,7 +143,7 @@ public function testEncoding()
         $response = $this->createClient()->sendRequest($request);
 
         $this->assertSame(200, $response->getStatusCode());
-        $this->assertContains('€', $response->getBody()->__toString());
+        $this->assertStringContainsString('€', $response->getBody()->__toString());
     }
 
     /**
@@ -157,7 +159,7 @@ public function testGzip()
         $response = $this->createClient()->sendRequest($request);
 
         $this->assertSame(200, $response->getStatusCode());
-        $this->assertContains('gzip', $response->getBody()->__toString());
+        $this->assertStringContainsString('gzip', $response->getBody()->__toString());
     }
 
     /**
@@ -173,7 +175,7 @@ public function testDeflate()
         $response = $this->createClient()->sendRequest($request);
 
         $this->assertSame(200, $response->getStatusCode());
-        $this->assertContains('deflate', $response->getBody()->__toString());
+        $this->assertStringContainsString('deflate', $response->getBody()->__toString());
     }
 
     /**
diff --git a/src/PhpUnitBackwardCompatibleTrait.php b/src/PhpUnitBackwardCompatibleTrait.php
new file mode 100644
index 0000000..05f094d
--- /dev/null
+++ b/src/PhpUnitBackwardCompatibleTrait.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Http\Client\Tests;
+
+use PHPUnit\Framework\TestCase;
+
+trait PhpUnitBackwardCompatibleTrait
+{
+    public static function assertStringContainsString(string $needle, string $haystack, string $message = ''): void
+    {
+        // For supporting both phpunit 7 and 8 without display any deprecation.
+        if (method_exists(TestCase::class, 'assertStringContainsString')) {
+            parent::assertStringContainsString($needle, $haystack, $message);
+        } else {
+            parent::assertContains($needle, $haystack, $message);
+        }
+    }
+}