This was our final full sprint, the next one being only a couple days, and designed for gathering our thoughts, doing a pseudo post mortem, and presenting what we learned through the project. With it, we have essentially finished the project. This last sprint was mostly dedicated to a final breakthrough on on our service and the use of Promises.
In the beginning of the sprint, it was filled with some level of frustration. Our team lacked extensive or comprehensive knowledge on Promises, and asynchronous coding in general. This led to some blind trial and error attempts at trying to get our service to work correctly. The main issue was that our tests were failing in ways that were confusing. The main way being that the code in our service functions were seemingly being skipped, not happening at all, or just not returning what was expected or wanted.
Due to this, it was hard to tell where we were going wrong. Because of this, we eventually began researching Promises more to discover what the issue was. Eventually in one of our bi weekly, in person meetings it was brought to my attention by Shane Rookey, a team mate, that the issue was not that were doing something wrong in our functions. The main issue was the way were testing them.
With a promise, due to it being asynchronous, it is unknown when it is resolved. That’s why you use the ‘.then’ method of a promise. This method executes a function when the promise resolves, or when it fails. When the promise resolves, then do this, essentially. We would use PouchDB’s methods (.get, .put, etc), handle it in a .then, and then attempt to return the response of those methods. And then in our tests we would use a simple line of code to see if the response was what we expected.
However, because what was being returned from the methods was a promise, doing anything with it without using .then just does not work. We were simply using a line of code that expected the responses from the methods to have a field called ‘ok’ to be true. But that is a regular synchronous line of code. It has to be placed in the .then to work. Anything done with a promise has to be done in a .then. And attempting to return it also does not work, as after something is done in a .then, it returns another promise.
You can not just write the functions in the service asynchronously and then just go on as normal when handling them in tests and other services or code. That was what we did not understand. Once that was understood, writing tests and actually seeing if our functions, well, functioned, was much easier. Another team by this point had managed to get a service running that would take patient data and store it using PouchDB. We both met during the sprint and decided we should focus on getting tests running for the service while they focused on getting a GUI to display stored data up and running.
In the end, I felt more could have been done if we had some more prior knowledge. And also, if there was a bit more of a comprehensive guide on using promises and how to work with them. Some more comprehensive documentation would have smoothed things out. Our team will strive to document all these things for future developers that work on the project, which will hopefully aid in alleviating a lot of frustration.