Does blockchain.info provide wallets and API service for testnet? This information is quite hard to find from their site.
It may be a bit late, but for others coming to this question, Blocktrail have a data and wallet API that supports both Bitcoin mainnet and testnet.
The API provides HD wallets with multi-signature transactions (allowing for full control over your coins should anything ever happen to Blocktrail), and there are currently SDKs for PHP, NodeJS and Python, with more coming soon.
There are also simple examples included in the SDKs to help you get started, a comprehensive API documentation, and a couple of working example projects:
1. Simple Bitcoin Wallet App
2. Simple Block Explorer
I am currently one of the core developers for this API
If you want to know all steps from create a wallet to broadcast a transaction in test net you can use of my step by step tutorial about this: step-by-step-create-and-broadcast-a-bitcoin-transaction-on-testnet