old_contents: // utils.js
  
  export function sumReturn(a, b) {
      return a + b
  }
  
  
new_contents: // utils.js
  
  export function sumReturn(a, b) {
      return a + b
  }
  
  export function productReturn(a, b) {
      return a * b
  }
  
  
subject: add not coverage function