I can not understand why it can’t pass test #9, #12, #13 and #14. When I make calculations by myself, answer is same like in the test, but when run it througth test, it is failed.
Thank you for your comment!
Now it can pass because with a help of people from the stackoverflow website, I solved this problem.
The problem was that calculator had wrong id’s for ‘+’ and ‘-’ buttons The tests are using the button id to press it, not its text.