Setting up a basic test transaction for p2p donation web app - API recommendation My question relates to the use case of trying to build a simple payment flow where one user (a donor) can donate directly to another user (a recipient) with Bitcoin.
To begin with, I would like to manually load up and input 2 addresses that respond to a Donate button and ideally get processed from test accounts on the Testnet blockchain.

I am new to bitcoin development and want to understand the underlying mechanics rather than immediately implementing a more sophisticated and abstracted plugin (e.g. Stripe).
Additionally, my preferred language is Ruby so I have been favouring APIs with Ruby SDKs.

So far I have a shortlist of the following APIs: 


Chain.com (https://chain.com/docs/ruby#bitcoin-transaction-overview) 
Blockcypher (http://dev.blockcypher.com/#payments) >> provide direct access to Testnet, not clear how would implement with others
Blockchain.info (can't link with current rep points) >> may force you to use their wallets


Has anyone worked with these and can provide guidance on which is best to implement the above use case? Other suggestions welcome. Appreciate this could be interpreted fairly broadly but I can try and specify further if you have questions.
In case anyone else faces this decision I decided to go with the Blockchain.info API (https://blockchain.info/).

Primary factors:


Easy to use ruby gem and interface - I was able to create wallets and transactions through invoking a few simple methods within my Sinatra app
Blockchain.info provide and utilise a stable wallet, recipient address which is easier and more intuitive to work with when starting out (e.g. easy to track senders and recipients against IDs)


Drawbacks:


I couldn't find a way to link in the Testnet blockchain so had to experiment with real Bitcoins
I was totally reliant on the Blockchain.info wallet and transaction structure. This was fine for a prototype/ experiment but for an actual MVP you would want to be able to integrate a wide range of wallet providers.