[5.6] Fixes starting of two database transactions in tests (#23132)

* Fixes starting of two database transactions in tests

* indentation fixed

src/Illuminate/Foundation/Testing/RefreshDatabase.php

@@ -6,8 +6,6 @@
 
 trait RefreshDatabase
 {
-    use DatabaseTransactions;
-
     /**
      * Define hooks to migrate the database before and after each test.
      *
@@ -61,4 +59,38 @@ protected function refreshTestDatabase()
 
         $this->beginDatabaseTransaction();
     }
+
+    /**
+     * Begin a database transaction on the testing database.
+     *
+     * @return void
+     */
+    public function beginDatabaseTransaction()
+    {
+        $database = $this->app->make('db');
+
+        foreach ($this->connectionsToTransact() as $name) {
+            $database->connection($name)->beginTransaction();
+        }
+
+        $this->beforeApplicationDestroyed(function () use ($database) {
+            foreach ($this->connectionsToTransact() as $name) {
+                $connection = $database->connection($name);
+
+                $connection->rollBack();
+                $connection->disconnect();
+            }
+        });
+    }
+
+    /**
+     * The database connections that should have transactions.
+     *
+     * @return array
+     */
+    protected function connectionsToTransact()
+    {
+        return property_exists($this, 'connectionsToTransact')
+                            ? $this->connectionsToTransact : [null];
+    }
 }