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=Using Helper Objects=

When writing a Squish test, it is often helpful to provide a helper object in your application code to provide information your test can’t easily access. A helper object, in this context, is a QObject that provides methods useful to Squish tests that is instantiated in the application for Squish to find. A helper object may be a good fit if you’re trying to verify application state that can’t easily be checked using native Qt and Squish functions.

As a contrived example, it might be useful to provide a helper object to get the color of a model rendered in a <span class="caps">QGLW</span>idget instead of trying to use a screenshot verification. Ideally a helper object’s methods should ''not'' have side effects, as an ideal Squish test should only be testing what a user can do with normal input.

==An Example C++ Helper Object==

The following class definition provides the method '''SquishHelper::help''', which Squish can invoke and get an integer result from. Note that '''SquishHelper::help''' is flagged as '''Q_INVOKABLE''', this is important! A method used by Squish must be accessible via Qt’s metaobject system, which means methods that are either slots or '''Q_INVOKABLE'''.

After defining the class, merely instantiate it somewhere and optionally give it a name if there may be multiple instances. Make sure that the QObject parent of the helper object is a <span class="caps">GUI</span> element Squish shows in its object tree for the application, such as the main window. This ensures that Squish can successfully look up the object later.<br />

==Using a Helper Object From Squish==

With the above helper object, looking up and invoking methods on the object is trivial. For instance, to look up the object and check the result of help in Python, you could do:<br />

This can be very useful to gain information about your application’s state, as you can use any C++ code you normally would, like in any unit test.

===Categories:===

* [[:Category:Tools|Tools]]
** [[:Category:Tools::Squish|Squish]]