Warn when classes are used in testing environment; this means tests aren't efficient.

app/Factory/TransactionFactory.php

@@ -40,6 +40,16 @@ use Log;
  */
 class TransactionFactory
 {
+    /**
+     * Constructor.
+     */
+    public function __construct()
+    {
+        if ('testing' === env('APP_ENV')) {
+            Log::warning(sprintf('%s should not be instantiated in the TEST environment!', \get_class($this)));
+        }
+    }
+
     use TransactionServiceTrait;
 
     /** @var User */