accessing the Litecoin testnet
It depends, do you want to run a full node and store the entire blockchain? You could run Litecoin Core: https://github.com/litecoin-project/litecoin. There are other implementations/installation options as well.

For an example of a project with a wallet, explorer, and full node, see:

https://github.com/litecoin-project/litecore

It implements:


Node - A full node with extended capabilities using Litecoin Core
Insight Lite API - A blockchain explorer HTTP API
Insight Lite UI - A blockchain explorer web user interface
Wallet Service - A multisig HD service for wallets
Wallet Client - A client for the wallet service
CLI Wallet - A command-line based wallet client
Angular Wallet Client - An Angular based wallet client
Copay - An easy-to-use, multiplatform, multisignature, secure bitcoin wallet