Image based testing basics
There are two approaches to black box GUI test automation, object oriented one and image based one.
Object
oriented testing tools
are tightly integrated with a programming platform, for example .NET,
C/C++, Java or alternatively the OS graphic interface (Win32 API, ...).
They can typically retrieve application GUI component
hierarchy and provide access to properties of individual GUI components
such as buttons, check boxes, text fields, drop downs etc. Advantage of
this approach is that you see the GUI structure from your test script
and you can easily navigate through it or verify whether it has the
expected content.
Disadvantages of object oriented tools are that they can not test
across different technologies and they often rely on certain platform
version (and keep forcing you to upgrade as new versions get released).
Image
based testing tools
analyze image of the tested application or the whole computer desktop.
They get it usually from the underlying operating system, for example
from the desktop image buffer or through attaching to the graphic
driver. Advantage of this approach is that the underlying technology is
irrelevant and the tool can test any application that displays on the
desktop of the operating system. Such a testing is also simple, close
to the end user experience and easy to learn even without programming
experience. It can also reveal layout
problems such as overlapping or ill fitting GUI components. Main
disadvantage of this approach is no access to the application GUI
component hierarchy. T-Plan Robot Enterprise is an image based testing tool. To overcome the the missing GUI hierarchy access it provides image comparison methods allowing to search for GUI components on the desktop and verify status of the tested application against image templates.
TIP: For
a complete comparison of test approaches read our article Image Based Versus Object
Oriented Testing.