Property-based tests and contracts

[rambip]

Like I presented in my previous issue, test coverage is misleading.

It would be a lot more valuable to write property-based tests, for example with fast-check

Another very valuable addition would be to add corresponding contracts (properties you want about a function) directly in the jsdocs. It could look like:

/**
 * @pre array.length > 0
 * @pre array.every((x, i) => i === 0 || x >= array[i - 1])
 * @post (result) => result === -1 || array[result] === key
 */
function binarySearch(array: number[], key: number): number {
  let lo = 0, hi = array.length - 1;
  while (lo <= hi) {
    const mid = (lo + hi) >> 1;
    if (array[mid] === key) return mid;
    if (array[mid] < key) lo = mid + 1;
    else hi = mid - 1;
  }
  return -1;
}

Then, the agent would translate it to a test and back.
I noticed the agent finds bugs a lot faster when invariants are written this way.