Currently we are developing the customizations required as per the new Shopify payments apps API for both the merchant onboarding and payments/refunds flow. As these 2 are being developed in parallel, can we simply test the merchant onboarding flow by configuring an 'app-url' and setting up a dev-store (for testing). This way we will be able to test the onboarding flow till the access token creation step. Please note, that we will not be configuring the payments urls yet.
Alternatively, is there another staging/sandbox utility that can be provided for us to test the various redirects from Shopify and the Shopify APIs?