Remove logic of state change from App component

[rmcreyes]

Describe the part of the code base that needs to be cleaned up
We currently have the logic for changing states in the App component. This makes it hard to test if state changes are being handled correctly.

Provide suggestions on how we can clean this up
Define a function somewhere else that contains all the logic for changing state, and import it into the App component. Write unit tests to make sure the function runs as expected.