fix various things

src/Illuminate/Cache/ArrayStore.php

@@ -100,6 +100,7 @@ public function forget($key)
     public function flush()
     {
         $this->storage = [];
+
         return true;
     }
 

src/Illuminate/Cache/FileStore.php

@@ -188,12 +188,14 @@ public function flush()
     {
         if ($this->files->isDirectory($this->directory)) {
             foreach ($this->files->directories($this->directory) as $directory) {
-                if(!$this->files->deleteDirectory($directory)){
+                if (! $this->files->deleteDirectory($directory)) {
                     return false;
                 }
             }
+
             return true;
         }
+
         return false;
     }
 

src/Illuminate/Cache/NullStore.php

@@ -93,7 +93,7 @@ public function forget($key)
      */
     public function flush()
     {
-        //
+        return true;
     }
 
     /**

src/Illuminate/Cache/RedisStore.php

@@ -170,7 +170,9 @@ public function forget($key)
      */
     public function flush()
     {
-        return (bool) $this->connection()->flushdb();
+        $this->connection()->flushdb();
+
+        return true;
     }
 
     /**