Add tests for detecting browser timezone name

test/php/library/Icinga/Util/TimezoneDetectTest.php

@@ -0,0 +1,49 @@
+<?php
+/* Icinga Web 2 | (c) 2017 Icinga Development Team | GPLv2+ */
+
+namespace Tests\Icinga\Util;
+
+use Icinga\Test\BaseTestCase;
+use Icinga\Util\TimezoneDetect;
+
+class TimezoneDetectTest extends BaseTestCase
+{
+    public function testInvalidTimezoneNameInCookie(): void
+    {
+        $tzDetect = new TimezoneDetect();
+        $tzDetect->reset();
+        
+        $_COOKIE[TimezoneDetect::$cookieName] = 'ABC';
+        $tzDetect = new TimezoneDetect();
+        $this->assertFalse(
+            $tzDetect->success(),
+            false,
+            'Failed to assert invalid timezone name is detected'
+        );
+
+        $this->assertNull(
+            $tzDetect->getTimezoneName(),
+            'Failed to assert that the timezone name will not be set for invalid timezone'
+        );
+    }
+
+    public function testValidTimezoneNameInCookie(): void
+    {
+        $tzDetect = new TimezoneDetect();
+        $tzDetect->reset();
+
+        $_COOKIE[TimezoneDetect::$cookieName] = "Europe/Berlin";
+        $tzDetect = new TimezoneDetect();
+        $this->assertTrue(
+            $tzDetect->success(),
+            true,
+            'Failed to assert that the valid timezone name is detected'
+        );
+
+        $this->assertSame(
+            $tzDetect->getTimezoneName(),
+            "Europe/Berlin",
+            'Failed to assert that the valid timezone name was correctly set'
+        );
+    }
+}