This is the last of the three part discussion on Browser Compatibility Testing.
Any strategy to test the compatibility of an application across browser-platform combination has to be considered with the understanding that the test is for checking the compatibility and not to establish that the application and its behaviour are exactly same in all the browsers and on all platforms (hardware, software and their combinations).
The first consideration should be the way the application is designed to support the different browsers and platforms. Applications are designed with a target user base, and information on their user profiles including operating systems, browser versions and the trends in the industry that will affect browser and platform usage. Based on these information, applications are designed for a set of 'most preferred browsers and a degraded support to another set of browsers. There are numerous browsers in the market, but only the browsers and platform combination that is either fully supported or are 'supported on a downgraded level' are tested as part of the compatibility tests.
So, the objective is to test and ensure that the application is correctly and consistently behaving in the set of preferred browsers and platforms and the degradation in matching the the way it is designed to. As an example, if the application needs to use a different style sheet on a lower version of IE, the test will verify that the user interface confirms to the styles specified for that version of IE.
The next is to identify a combination of platforms and browsers that needs to be tested. Depending on the technology and components that are used in an application, we can establish an 'equivalence' among browsers in the way they handle components and reduce the test combinations. Once the test combination is reviewed with the design/development team agreed upon, tests that cover the breadth of the application and UI components is designed. Generally, the scenarios are a subset of the functional scenarios, but are focused more on UI characteristics that functionality.
On many occasions, people rush to automate the tests because they have to run the same test on many browsers and operating systems. But, remember that the expected results are going to be different on the preferred browser(s) and the less supported ones and so the 're-usability' that is counted to justify the automation investment may not be true. But, there are several cases where automating such tests make complete sense.
There are several tools that support varying levels of browser compatibility testing. Even functional testing tools like HP QTP and TOSCA (from Tricentis)can do a limited amount of browser compatibility testing. Both these tools claim to come up with support for newer versions for FireFox (currently supports only v3.6) and also Google Chrome some time in December. With that, they all should be able to do a certain level of compatibility testing, at least with the 'most preferred browsers'. Open source tools like Selenium also can support browser compatibility tests.
The best tool I have come across is Eggplant (http://www.testplant.com/) which is an image based automation which uses a proprietary technology to recognise images. It also is in dependant of the operating system as it uses a VNC connection to the various machines that host the various versions of browsers on which the tests need to run.
Automation or no automation, the key to success is identifying the expected behaviour in the target and supported browsers and designing an optimum number of tests that cover the GUI objects to validate the expected behaviour.
I test. Therefore I am.
