message: Add tests over Selection startsBefore()
  I wasn't sure and needed to check. This test will give me the answer
  next time!
diff: @@ -72,4 +72,24 @@ describe("Selection", () => {
  expect(extendedSelection).toStrictEqual(new Selection([0, 10], [3, 10]));
  });
  });
  +
  + describe("startsBefore", () => {
  + it("should return true if selection starts before given one", () => {
  + const selection = new Selection([1, 4], [1, 8]);
  + const anotherSelection = new Selection([2, 4], [2, 5]);
  +
  + const result = selection.startsBefore(anotherSelection);
  +
  + expect(result).toBe(true);
  + });
  +
  + it("should return true if selection starts at the same position as given one", () => {
  + const selection = new Selection([1, 4], [1, 8]);
  + const anotherSelection = new Selection([1, 4], [2, 5]);
  +
  + const result = selection.startsBefore(anotherSelection);
  +
  + expect(result).toBe(true);
  + });
  + });
  });
  