When you make a few more changes and commit

vim test.rb

git commit -am 'make more changes'

your project history diverges as shown in the diagram below

                                                          _**Diverged branch histories**_

Your workflow:

You created a new branch, testing, switched to and did some work on it, and then switched back to your main branch master, and did some other work.

NB: Both of these changes are isolated in separate branches: once ready with work on either branches, you can switch back and forth between the branches and merge them together.