In my earlier I post I talked about not being very sure that a method I wrote for one of the Stanford iOS Programming course assignments was really embracing Swift as a language. I then posted about using Swift’s unit test framework that would make any refactoring easier and better.
And so on to the refactoring…
Well, with a fresh day came a fresh eye, and there was not too much I could really do to make the method more Swift than C/C++. I ended up mainly folding some let statements into inline expressions. Not exactly hard, but when all was completed I think the code is more or less as tight as it could be and still easily readable – opinions to the contrary are very welcome.
In an earlier blog post I wrote about my solution to one of the homework assignments for Stanford University’s iOS programming course. My conclusion was that, while the code worked, it seemed a little bit too C-like and not really embracing some of the elegance of the Swift programming language.
My intention is to rewrite the code and see if I can get it looking somewhat more Swifty. But of course in doing that I don’t want to break it – there’s a lot of different cases the CalculatorBrain has to handle. This is a classic scenario that can be solved using automated unit testing.
When you create a new application project in XCode, as well as the main build target you get given a test target with boilerplate code for using XCode’s unit testing framework. It is simple to use – just add new functions to the test class, and use XCTAsserts to ensure the right results.
Here is a usful snippet if you want a way to get the number of rows in each table in your database. I use this in an admin-only page of the web application to provide some at-a-glance statistics. It is also really useful in unit tests for checking the correctness of business logic that may create new entries in several tables in one transaction.
To aid my unit testing I needed to populate a database with a load of test data. This data needs to be generated by some of the less technical guys on the project and so exporting CSV (Comma Separated Values) files from Excel seemed a sensible approach. So I then cast around for any existing code that would save me having to write a robust CSV parser. The search turned up this on CodeProject:
The neat thing about it is that you can get field values either by index position or column name, assuming you put column headers in your file. The column name feature really helps out with maintainance of the test data as we evolve and vary the schema slightly – we can insert columns with no worries about upsetting existing reader code.
It’s easy to use and install in your own project, and the CodeProject article describes the basic usage pattern. At the moment it is just linked in to the unit test framework, but is so useful I will probably make it a part of the core application libary to facilitate importing data from customers as we anticipate some of our customers could have thousands of records to import when they move to our system.
Just a quick note about a little problem I found using Nunit (2.2.9, but affects earlier revisions too).
After a bunch of edits to my project, I suddenly started getting messages from NUnit GUI “could not load file or assembly nunit.core”. Try as I could, this would not go away. This included everything from reinstalling NUnit to tracking DLL loading via SysInternal’s Process Explorer tool.
My project is non trivial – a top level solution containing an ASP2 web project, a couple of library DLL’s for the business logic, a unit test executable, and a testing helper library to help cross reference test results against direct SQL calls. As I’ll be writing about in another post shortly, incorporating unit testing into an ASP project is a pain in the rear and so I had been restructuring things. My natural assumption based on the error message was I had messed up something in the linking/referencing.
But it turned out to be an error in the application config file – for some reason NUnit reports this as a DLL missing, not that you have mistyped a bit of config text. I simply had a closing tag in the wrong place – still syntactically correct, however.
This link is by someone else who hit the exact same problem, and he has written about in more detail.
So remember folks: never assume a system generates the correct error message for all circumstances.