Why we use Test.starTest and Test.stopTest in Salesforce?

Hi Shaharyar,

Test.startTest and Test.stopTest are used for asynchronous apex, like Batch Apex and Future calls. Calling method(s) between Test.startTest and Test.stopTest ensure that any asynchronous transactions finish executing before Test.stopTest() exits. This means, that if you use System.asserts after Test.stopTest, you'll have an accurate representation of your test. Otherwise, if you called System.assert before Test.stopTest, or if you didn't use Test.startTest / Test.stopTest, then you couldn't gaurantee that the batch or future transaction was complete.

startTest()

Marks the point in your test code when your test actually begins. Use this method when you are testing governor limits.

Usage

You can also use this method with stopTest to ensure that all asynchronous calls that come after the startTest method are run before doing any assertions or testing. Each test method is allowed to call this method only once. All of the code before this method should be used to initialize variables, populate data structures, and so on, allowing you to set up everything you need to run your test. Any code that executes after the call to startTest and before stopTest is assigned a new set of governor limits.

stopTest()

Marks the point in your test code when your test ends. Use this method in conjunction with the startTest method.

Usage

Each test method is allowed to call this method only once. Any code that executes after the stopTest method is assigned the original limits that were in effect before startTest was called. All asynchronous calls made after the startTest method are collected by the system. When stopTest is executed, all asynchronous processes are run synchronously.

Hope this helps.