//Test for 1000 times to make every value is unique and of size 13 digits
def noOfSamples = 1000
//Below list can hold only unique values
def list = [] as Set<String>
noOfSamples.times {
	//generate a 13 digit string and put in the list
	list << System.currentTimeMillis().toString()
	//wait for a milli second inorder to generate new unique value just for testing; in real time you won't land into this
	Thread.sleep(1)
}
//Since all we are storing fixed number of values, if there are non-unique, size won't match; hence the test
assert noOfSamples == list.size(), 'Not all unique values'
//Check every value is of 13 digit lenth
assert list.every {13 == it.size()}, 'There are generated values not of length 13 digits'

//Do you want to see the generated values? Uncomment below line
//list.each {println it}