diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 2ec6f6e..de6a4ce 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -5,7 +5,9 @@
 <phpunit  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/6.3/phpunit.xsd"
          backupGlobals="false"
-
+         convertErrorsToExceptions="true"
+         convertNoticesToExceptions="true"
+         convertWarningsToExceptions="true"
          colors="true"
          bootstrap="vendor/autoload.php"
 >
diff --git a/tests/Sikofitt/Tests/UserAgentTest.php b/tests/Sikofitt/Tests/UserAgentTest.php
new file mode 100644
index 0000000..3a72f14
--- /dev/null
+++ b/tests/Sikofitt/Tests/UserAgentTest.php
@@ -0,0 +1,109 @@
+<?php declare(strict_types=1);
+
+/*
+ *     This file is part of sikofitt/user-agent
+ *
+ *     Copyleft (C) 2017  http://sikofitt.com sikofitt@gmail.com
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Sikofitt\Tests;
+
+use PHPUnit\Framework\TestCase;
+use Sikofitt\UserAgent\UserAgent;
+
+class UserAgentTest extends TestCase
+{
+    private $zts;
+    private $arch;
+
+    public function setUp(): void
+    {
+        $this->zts = (bool)PHP_ZTS ? '-zts' : '';
+        $this->arch = 9223372036854775807 === PHP_INT_MAX ? 'x86_64' : 'i386';
+
+        parent::setUp();
+    }
+
+    public function testExtendUserAgent(): void
+    {
+        $userAgent = new class extends UserAgent {
+            protected static $format = 'PHP/%d.%d.%d (%d)';
+            protected static $params = [
+                PHP_MAJOR_VERSION,
+                PHP_MINOR_VERSION,
+                PHP_RELEASE_VERSION,
+                PHP_VERSION_ID,
+            ];
+        };
+
+        $expected = sprintf(
+            'PHP/%d.%d.%d (%d)',
+            PHP_MAJOR_VERSION,
+            PHP_MINOR_VERSION,
+            PHP_RELEASE_VERSION,
+            PHP_VERSION_ID
+        );
+        $actual = $userAgent::create();
+        $this->assertSame($expected, $actual);
+    }
+
+    public function testFailure(): void
+    {
+        $userAgent = new class extends UserAgent {
+            protected static $format = '';
+            protected static $params = [];
+        };
+
+        $this->assertNotSame(UserAgent::create(), $userAgent::create());
+        $this->assertNotSame(UserAgent::create(), '');
+    }
+
+    public function testDefaultUserAgent(): void
+    {
+        $format = 'PHP/%d.%d%s-%d (%s; %s %s) PHP/%s%s; %s (%s)';
+        $params = [
+          PHP_MAJOR_VERSION,
+          PHP_MINOR_VERSION,
+          $this->zts,
+          PHP_VERSION_ID,
+          'sikofitt/user-agent',
+          PHP_OS_FAMILY,
+          $this->arch,
+          PHP_VERSION,
+          $this->zts,
+          $this->getGuzzleVersionString(),
+          'https://packagist.org/sikofitt/user-agent',
+        ];
+        $expected = sprintf($format, ...$params);
+
+        $userAgent = UserAgent::create();
+        $this->assertSame($expected, $userAgent);
+    }
+
+    private function getGuzzleVersionString(): string
+    {
+        /** @noinspection ClassConstantCanBeUsedInspection */
+        if (class_exists('GuzzleHttp\Client')) {
+            /** @noinspection PhpUnnecessaryFullyQualifiedNameInspection */
+            $guzzleClient = new \GuzzleHttp\Client();
+            $guzzleHeaders = $guzzleClient->getConfig('headers');
+            $guzzleUserAgent = $guzzleHeaders['User-Agent'];
+            return trim(explode('php', strtolower($guzzleUserAgent))[0]);
+        }
+
+        return '';
+    }
+}