Imagine you open your google map view and look for a place you want to go, 
you immediately see closeby restaurants, you see options for the commute; 
from some leading travel providers, and see so many options at your 
fingertips. We all know they are not google products but google manage to
show it. They use the exposed APIs of these providers.

Even before the UI built or under development, API testing becomes very 
important, we are testing them repeadetly with different data combinations
makes it a very suitable case for automation.