Add guidance for test transactions

[yashrajd]

Describe your content request
Content & designs for test transaction features in wallets

Rationale

• test transactions are a common usage pattern in bitcoin as well as fiat transactions
• this was recently discussed in a podcast episode around 22 mins
• test transactions are great way silent payments users to validate and feel comfortable about sending bitcoin to a different address than that provided by the receiver

Suggestions
@rabbitholiness and max pain truly created prototypes (here and here), which could be used to craft content for the issue.

Happy to work on this... actively taking suggestions for where in the guide this content should go.

[GBKS]

The Bitcoin Core App design docs now have some mocks and details on this feature idea.

[yashrajd]

Good to see! Looks like 2.x will be my fav releases of all time with assumeutxo, silent payments and test transactions getting in! :)

[yashrajd]

Taking this on, please assign me.

There seem to be 2 methods to do this: a) small amount test with high(est) fees (since light clients might not be able to see mempool txns and b) full amount with RBF but needs to be confirmed (no extra fees but might not work where receiver can't see payments in the mempool)

Based on the mocks mentioned above, here are the ux points I'd like to mention:

• use cases: 1) large payment (method (a) seems appropriate) 2) first time sending to user's silent payment address (method a or b)

• prompt the user during send flow in the appropriate scenarios (large amount or first time sending to a sp-addr)

• inform users about extra fees involved if any

• inform users they need to be able to communicate with the receiver

• make the confirm payment CTA ( a card or banner) easy to see and access

• maybe notify/remind the user

• allow the user to revert the payment (only viable for RBF method)