diff --git a/tests/src/Unit/CheckDnsServiceTest.php b/tests/src/Unit/CheckDnsServiceTest.php
new file mode 100644
index 0000000..a5149c8
--- /dev/null
+++ b/tests/src/Unit/CheckDnsServiceTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace Drupal\Tests\check_dns\Unit;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\check_dns\CheckDnsService;
+
+/**
+ * @coversDefaultClass \Drupal\check_dns\CheckDnsService
+ */
+class CheckDnsServiceTest extends UnitTestCase {
+
+  /**
+   * The tested check dns service.
+   *
+   * @var \Drupal\check_dns\CheckDnsService
+   */
+  protected $checkDnsService;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    $this->checkDnsService = new CheckDnsService();
+  }
+
+  /**
+   * Tests the validateEmail() method.
+   */
+  public function testIfEmailDomainIsValid() {
+    $mail = 'test@gmail.com';
+    $this->assertTrue($this->checkDnsService->validateEmail($mail));
+  }
+
+  /**
+   * Tests the validateEmail() method.
+   */
+  public function testIfEmailDomainIsNotValid() {
+    $mail = 'test@suchafakedomain.com';
+    $this->assertFalse($this->checkDnsService->validateEmail($mail));
+  }
+
+}