Why Are Automated GUI Tools So Fragile?

Question

For about a year a half, I've been working with SilkTest, which is a GUI automation tool, for both desktop and web applications. It simulates mouse and keyboard inputs, which eventually simulate end user behaviour. However, I find that it is a bit flaky; Button.Click() or DialogBox.Close() method calls that work just fine 9 times in a row seem to fail on a 10th call, only to go back working on the 11th. Normally I would just chalk this up to a quirk with SilkTest (or the application under Test, or the OS, or what have you) but then I see that there are similar issues with other GUI automation tools like Selenium:

Selenium Click() fails with Anchor Elements

Selenium Click() fails clicking button object

I know that for desktop apps, each GUI control/dialog has a tag element associated with it (at least in Windows-based GUIs) and that for web pages there is the domain object model hierarchy of page elements. My guess is that these tools sometimes run into issues navigating these hierarchies and finding unique elements and controls. But what is going on here? SilkTest is a relatively old, commercial software package while selenium is relatively new, open source and constantly evolving. The fact that they both can have similar problems raises a couple of flags with me.

Also, is this the case with other GUI test tools? Or have I just had a somewhat unusual experience?

Answer 1

There are 2 things here that you are talking about, first the concept of finding an object in the application under test that you want to automate. Your description of how SilkTest (and other tools) does this is quite accurate, i.e. as long as there is something that the automation software can use to identify the control then you are fine.

The second thing is why does the automation itself fails randomly, since the tool has not reported that it could not find the control then it must think that it sent the appropriate action to the application, e.g. a Click or a Type. This could be that the application is not ready to accept the action that you are sending it, this is similar to you attempting to click on something "before it was ready", in this case the application can decide to buffer the input or to discard the input.

So, how do you fix this? One way would be to use the capabilities of the tool to try to work out when the application is ready for input rather than sending it a stream of input blindly. SilkTest has capabilities that allow for you to do this (as does TestPartner). I cannot comment on Selenium as it is something I have not used.

A simple way of testing this would be to insert a pause for a couple of seconds before the offending action, then run this in a loop to see whether this solves the problem, if this is the case then it is your problem. If this does not fix the issue then there is something else going on that you need to contact the vendor of the testing tool.

Remember that applications are getting more and more complex, i.e. multi-threading, communications, any one of these could cause the automatic syncronisation to fail causing actions to fail.

Hope that helps.