Focus a JS Test

A vital testing skill is focusing a test. When iterating on a failing test, we want that test under microscope. The way I do this in JavaScript is .only : import { describe , expect , test } from 'vitest' ; import { sum } from './sum.js' ; test ( 'adds 1 + 2 to equal 3' , () => { expect ( sum ( 1 , 2 )). toBe ( 3 ); }); describe . only ( 'adding fours' , () => { test ( 'adds 4 + 4 to equal 8' , ()…