Our ProFitOro application works just fine, doesn't it? We have opened it so many times in the browser, we have checked all the implemented features, so it just works, right? Yes, that's true. Now go to your settings page and try to change the values of the timer to something strange. Try it with negative values, try it with huge values, try it with strings, and try it with empty values…do you think that can be called a nice user experience?
Have you tried to create a strange workout? Have you tried to introduce a huge workout name at its creation and see how it displays? There are thousands of corner cases and all of them should be carefully tested. We want our application to be maintainable, reliable, and something that offers an amazing user experience.