Umm... nope.
Just solve thousands of katas (and view how they do testing) and you will know what to do

Ok, seems that you are still stuggling
Here are what you at least need to do
In preload

const usercode = module.require('fs').readFileSync('/home/codewarrior/solution.txt','utf8'),lenlimit = 12

In final test

Test.describe('Code Length Check',() =>
{
	Test.it(`Should be less than ${lenlimit} charcters`,() =>
	{
		Test.expect(usercode.length < lenlimit,`${usercode.length} should be less than ${lenlimit}`)
	})
})

well, only thing that is hard is to see the pattern imho ;-) i have chosen 7 kyu

You can solve some existing 'One line' katas and find out what they did