Add some initial tests for the new SimpleSAML\Locale\Language class.

tests/lib/SimpleSAML/Locale/LanguageTest.php

+<?php
+
+namespace SimpleSAML\Test\Locale;
+
+use SimpleSAML\Locale\Language;
+
+class LanguageTest extends \PHPUnit_Framework_TestCase
+{
+
+
+    /**
+     * Test SimpleSAML\Locale\Language::getLanguageCookie().
+     */
+    public function testGetLanguageCookie()
+    {
+        // test it works when no cookie is set
+        \SimpleSAML_Configuration::loadFromArray(array(), '', 'simplesaml');
+        $this->assertNull(Language::getLanguageCookie());
+
+        // test that it works fine with defaults
+        \SimpleSAML_Configuration::loadFromArray(array(), '', 'simplesaml');
+        $_COOKIE['language'] = 'en';
+        $this->assertEquals('en', Language::getLanguageCookie());
+
+        // test that it works with non-defaults
+        \SimpleSAML_Configuration::loadFromArray(array(
+            'language.available' => array('xx', 'yy', 'zz'),
+            'language.cookie.name' => 'xyz'
+        ), '', 'simplesaml');
+        $_COOKIE['xyz'] = 'yy';
+        $this->assertEquals('yy', Language::getLanguageCookie());
+    }
+}