Add an example in Introduction of Testing

[rohan09-raj]

• In the Introduction Page of Testing, add a sub-heading How to write tests?
• Under this sub-heading, add a small example of a Test to make the flow clear and help the reader to get started with testing.

[rohan09-raj]

@jenweber Would like to work on this issue. Can you please assign it to me ??

[locks]

Hi @rohan09-raj. Did you end up working on it?

[Abhay5855]

Hey, @locks Would like to work on the issue. Can you please assign it to me?