When to use Test.isRunningTest() in Salesforce Apex Class?

Hi Pranav,

isRunningTest()

Returns true if the currently executing code was called by code contained in a test method, false otherwise. Use this method if you need to run different code depending on whether it was being called from a test.

Other scenarios:
1) To ensure the trigger doesn't execute the batch if Test.IsRunningTest() is true, and then test the batch class with it's own test method.
2) Testing callouts - in your callout code you check to see if you're executing within a unit test context by checking Test.isRunningTest() and instead of getting your callout response from an HttpResponse.send() request, you return a pre-built test string instead.