OCUnit XML File Output

by Jason Foreman — Oct 24, 2009

In the world of Mac OS X programming, OCUnit reigns supreme as the unit testing library of choice. Apple has put a great deal of work into ensuring that OCUnit is tightly integrated into the standard development workflow with Xcode. Unfortunately many other tools–such as continuous integration servers or test metric tools–expect test output in an XML file, typically in the format of the jUnit output from the Java Ant build tool. OCunit does not provide xml file output by default, but adding support for it is quite easy.

The Goal

Build servers such as Hudson have the ability to process test output and generate trend graphs and notifications. Most such tools rely on having the output in a particular format, often the jUnit format. OCUnit by default only prints its output to the console.

The jUnit XML format produced by Ant is horribly undocumented. It does seem to be a rather simple format though, which basically looks like this:

<testsuites>
    <testsuite name="MyTestSuite">
        <testcase name="MyTestCase.testFooMethod"></testcase>
        <testcase name="MyTestCase.testBarMethod">
            <failure>Exception, blah blah blah</failure>
        </testcase>
    </testsuite>
</testsuites>

The Means

OCUnit does offer a few hooks which can be used to follow test execution. A quick peek around the SenTestingKit framework headers–found in /Developer/Library/Frameworks/SenTestingKit.framework/Headers– shows a couple of obvious ways to watch test execution. The first is the SenTestObserver class, and the second is a collection of NSNotifications that SenTestObserver is presumably based upon.

SenTestObserver

The SenTestObserver class defines a set of methods that will be called at the beginning and end of both test suites and test methods. This looks like a perfect solution, but it is completely non-obvious how to actually use a subclass of SenTestObserver. Also, there are at least some reports that SenTestObserver is broken.

Notifications

Since there appear to be some issues with using SenTestObserver directly, the next step is to directly observe the set of notifications upon which it is based. The following notifications are defined in the SenTestingKit headers:

• SenTestSuiteDidStartNotification
• SenTestSuiteDidStopNotification
• SenTestCaseDidStartNotification
• SenTestCaseDidStopNotification
• SenTestCaseDidFailNotification

Using these notifications it is possible to create a class that can write to an XML file as test execution progresses. The only interesting task remaining is to load the class before test execution starts, which is easily accomplished using a gcc constructor attribute.

The Result

BPOCUnitXMLReporter is a small bit of code that records OCUnit test execution and writes it to an XML file. The code, along with a small sample project, is available on github and can be easily added to any OCUnit test bundle. Simply add the BPOCUnitXMLReporter.m file to the test bundle target, and every time the tests run a file ocunit.xml will be written with the test results. Contributions are certainly welcome, so fork away!