Added test for custom predis client

tests/PredisCustomClient.test.php

@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * @author Khoa Bui (khoaofgod)  <khoaofgod@gmail.com> http://www.phpfastcache.com
+ * @author Georges.L (Geolim4)  <contact@geolim4.com>
+ */
+
+use Phpfastcache\CacheManager;
+use Phpfastcache\Helper\TestHelper;
+use Phpfastcache\Drivers\Predis\Config as PredisConfig;
+use Predis\Client as PredisClient;
+
+chdir(__DIR__);
+require_once __DIR__ . '/../vendor/autoload.php';
+$testHelper = new TestHelper('Predis custom client');
+
+try{
+    $predisClient = new PredisClient([
+      'host' => '127.0.0.1',
+      'port' =>  6379,
+      'password' => null,
+      'database' => 0,
+    ]);
+    $predisClient->connect();
+
+    $cacheInstance = CacheManager::getInstance('Predis', (new PredisConfig())->setPredisClient($predisClient));
+    $cacheKey = 'predisCustomClient';
+    $cacheItem = $cacheInstance->getItem($cacheKey);
+    $cacheItem->set(1337);
+    $cacheInstance->save($cacheItem);
+    $cacheInstance->detachAllItems();
+    unset($cacheItem);
+    if($cacheInstance->getItem($cacheKey)->get() === 1337){
+        $testHelper->printPassText('Successfully written and read data from outside Predis client');
+    }else{
+        $testHelper->printFailText('Error writing or reading data from outside Predis client');
+    }
+}catch (\RedisException $e){
+    $testHelper->printFailText('A Predis exception occurred: ' . $e->getMessage());
+}
+
+$testHelper->terminateTest();