function padEmptyArgs(count, replacements) {
  /** @type {function(MatrixEntry): MatrixEntry[]} */
  let expand = (entry) => {
    let expanded = [entry];
    let { args, expected } = entry;
    if (args.length < count) {
      replacements.forEach((replacement) => {
        expanded.push({ args: padArgs(args, count, replacement), expected });
      });
    }
    return expanded;
  };
  return expand;
}
Creates additional matrix entries with alternative empty values.
@param {number} count
@param {any[]} replacements