Add new tests for transformers.

app/Models/PiggyBankEvent.php

@@ -35,6 +35,10 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
  * @property int                $id
  * @property Carbon             date
  * @property TransactionJournal transactionJournal
+ * @property string             $amount
+ * @property Carbon             created_at
+ * @property Carbon             updated_at
+ *
  */
 class PiggyBankEvent extends Model
 {