As mentioned [in the last review](https://github.com/Shopify/active_merchant/pull/1027#discussion_r9594117), this `post = options` assignment is incorrect - when you change the `post` variable in this method it may also affect whatever variable was given as `options` in the methods caller.

The correct way to go about this is to start with `post` as an empty hash, and then add keys to it that you allow to be passed from options.

For an example of the correct pattern to use, look at the way the SagePay gateway #refund method constructs its post variable [here](https://github.com/Shopify/active_merchant/blob/1e8658bc245e1524f4628fe80d76a19001ec1cdc/lib/active_merchant/billing/gateways/sage_pay.rb#L108-L118).

(same comment applies to your #capture as well)