I recently posted an article called Setting up and using Code Coverage. As I mentioned there, code coverage is useful for seeing what portions of your code have been exercised. What code coverage can’t do though is to ensure functional correctness – this is where functional coverage comes into play. Functional coverage allows you to determine when you have exposed your code to a sufficient enough set of stimulus, including hitting corner cases, that you have a high confidence in its functionality.
My background includes experience as a hardware verification engineer, where the teams I was part of used both code coverage and functional coverage as essential tools in test development. In the Wikipedia section on SystemVerilog (a hardware description and verification language) there is a nice write-up on Coverage where the difference between code coverage and functional coverage is discussed.
What is a Coverpoint?
I wanted to employ some functional coverage as a guide to my unit test development. In the SystemVerilog language mentioned above, they have the concept of coverpoints and covergroups (group of coverpoints). I found a nice document called SystemVerilog Testbench Automation Tutorial where there is some good information about these concepts starting in the section titled “Functional Coverage”.
A coverpoint is essentially a measurement point where an event (such as values taken on by a variable) can be recorded, along with bins for how many times specific values (or range of values) occurred for that event.
I have an application that I’m working on that uses Parse (a service that lets you persist objects in the cloud, perform queries, etc.). Calls to the Parse APIs are initiated from the main thread and dispatched to the global queue, thus completion of these calls happens asynchronously.
I wanted to write some unit tests to verify the functionality of my methods that interface with Parse.
Referencing the View Controller
My initial view controller is called EntryViewController. This view controller instances a class called ParseConnection which serves as a model for all my Parse interactions. All calls to methods in ParseConnection from EntryViewController are dispatched to the global queue. Within ParseConnection, all the API calls are made synchronously in this background queue.
My first challenge was how to get a reference from my unit tests to EntryViewController. I wanted to do this from the instance setUp method in my test suite class called ContactsOnlineBasicUnitTests, and store this reference in a property. This setUp method is called before each test case is run.
@interface ContactsOnlineBasicUnitTests ()
@property (strong, nonatomic) EntryViewController *entryViewController;
In my last post I talked about how to setup for Code Coverage and made a reference to unit testing. In this article I wanted to share my experience with setting up to run unit testing.
A great place to start is the Apple document Xcode Unit Testing Guide.
Setup target and initial test suite
Choose File > New > Target …
In the iOS section, select Other, then select the Cocoa Touch Unit Testing Bundle template.
Since my app is called ContactsOnline, I’ll name my product (new target) ContactsOnlineBasicUnitTests.
This creates a test suite by the same name ContactsOnlineBasicUnitTests.m, within a group called ContactsOnlineBasicUnitTests.
Unit-test targets define one or more test suites.
My background includes many years of Verification work on complex computer and graphics chips, so I was happy to learn that Xcode had some support for testing and code coverage. Code coverage is very useful as a guide to developing tests to let you see what portions of your code have been exercised.
The following example code coverage results are displayed using the tool CoverStory. They show what percentage of various classes have been exercised in the left pane, along with details about which lines in a particular file have not been covered in the right pane (highlighted in red).