Why do we write startTest() and stopTest() methods in Test Class in Salesforce?

Hello Shradha

Test.startTest is used to mark the point in your test code when your test actually begins. Each test method is allowed to call this method only once. After you call this method, you get a fresh set of governor limits for the remainder of the test until you call Test.stopTest.

Test.stopTest is used to marks the point in your test code when your test ends. Each test method is allowed to call this method only once. After calling this method, any post assertions are done in the original context.