As far as what LTS contains and how you use it, I suggest you refer to this Getting Started With Lightning Testing Service post by Christophe Coenraets from the Developer Relations Group. He does a great job of getting you started building your first test suite.
In this post, I will just highlight the super important things you need to know about working with LTS:
- You do not install or use LTS in production. Seriously! This is just for development environments and even better it is for scratch orgs that you create using SalesforceDX.
- LTS includes sample code to get you started. This includes not only the Jasmine and Mocha wrappers, but a Lightning App called JasmineTests.app that you can use to jump start your testing. Just follow the instructions in Christophe’s blog post and you should be up an running in no time.
- This is the most important tip: Do not use LTS to test your server code. Keep your client and server-side testing separate. When calling Apex server methods that insert records with LTS, the data that is created is NOT rolled back. You have to be responsible for rolling back the data yourself. You can still mock the server call and an example of this is provided in Christophe’s blog post as Scenario #6. This is the recommended and best way for you to test the server code in your lightning Components. You can still create (and you actually still need to) regular unit tests to test that your Aura methods work as expected.
Ok, that’s it.
Hope it helps and good luck in your journey towards becoming an AWESOME Lightning Developer using Lightning Testing Service.