Checking if date is valid in javascript get `RangeError: Invalid time value` testing it

I created this function to check if the date is valid or not:

function isValidDate(dateObject){
  if(!dateObject) return;
  
    return new Date(dateObject).toString() !== 'Invalid Date';
}
console.log(isValidDate('not valid time')) // false

This function works good, but trying to test it with jest i get this error: RangeError: Invalid time value, i suppose that this happens because the argument is a string and it pass the if(!dateObject) return;.
Question: How to avoid this error in my case?