Для решения вашей задачи мне пришлось использовать Math.round() после деления отрезка на 2, когда в бинарном поиске (хоть в той же ссылке на Вики, которую вы прикрепили) необходимо использовать Math.floor().
Плюс по вашей логике в игре от 1 до 10 к примеру если отвечаешь на guess 5 - меньше, то рассматривается диапазон от 1 до 5, когда на самом деле должен рассматриваться уже диапазон меньше 5: от 1 до 4!

method description, we have in task:
"lower()
this method is called if prev call of guess() returned number which is lower than answer"

test example (the very first test in guessing-game.spec.js):

it('should guess number 409 with max value 4048', () => {
const number = 409;
const game = new GuessingGame();
game.setRange(0, 4048)

let result = game.guess();
game.lower();
result = game.guess();
game.lower();
result = game.guess();
game.lower();
result = game.guess();
...

As you can see, method game.lower() called when it shoudn't (first assumption will be 2024 > 409), hence it didn't work properly.

the whole sequence of testing calls of
game.lower();
game.greater();
methods is reverted.

So maybe you should change method definitions?

Add changes to README.md

Change this:

setRange(min, max)
this method accepts min and max value of range of number to guess

To this:

setRange(min, max)
this method accepts min (not included) and max (included) value of range of number to guess,
in mathematics that would be (min, max]

Why do so

The proposed changes leave less room for ambiguity.
The solution that passes all tests does not find the min value of method setRange,
no matter how many times method lower is called.
It implies that min is not included in the searching range.
Possibly because of that a common binary search algorithm that can actually find min won't pass most of the tests.

The solution that passed 100% of the tests won't find the min value 0 of setRange(0, 4)

const game = new GuessingGame;

game.setRange(0, 4);

console.log(game.guess()); // 2
game.lower();

console.log(game.guess()); // 1
game.lower();

console.log(game.guess()); // 1
game.lower();
console.log(game.guess()); // 1