Why shouldn't we write @isTest  before the class, for the RandomContactFactory trialhead challenge? The Example shown in the same trialhead for the class 'TestDataFactory'  has @isTest before the class.

Why shouldn't we write @isTest  before the class, for the RandomContactFactory trialhead challenge? The Example shown in the same trialhead for the class 'TestDataFactory'  has @isTest before the class.

hello,

i am a newbie to salesforce and trying to complete this trailhead challenge and unable to find a way through apex to generate this method for creating new contacts with unique id. as one requirement to pass the challenge is "The 'generateRandomContacts' method must be capable of consistently generating contacts with unique first names."

If somebody successfully completed the task kindly help me.

regards,