Recently bloomreach is used by our client for CMS system. The website is ecommerce. But need to know how can I develop a layout, a content design and add that component in bloomreach. like how to integrate bloomreach with git repo , the entire process and how to unit test that component based on the different input values that one can provide in experience manager window. Please suggest.
My first suggestion is for you to sign up for an official training 
We have a documentation site that includes tutorials. Please see:
For unit testing, this is a useful tool:
You use git but initialising a git repo on your project. Don’t include the target directories.