Squish/Using Helper Objects

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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 QGLWidget 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.

#include <QObject>

class SquishHelper : public QObject
 SquishHelper(QObject* parent);

Q_INVOKABLE int help() const; //only offer a non-const method if you have a good reason

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 GUI 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.

SquishHelper* helper = new SquishHelper(this);

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:

helper = findObject("{name='Helper1' type='SquishHelper'}")
test.compare(helper.help(), 0)