Chapter 4: Replaying GUI Events

In this chapter, we will show how to simulate a GUI event, and how to store a series of GUI events as well as replay them on a widget.

The approach to storing a series of events and replaying them is quite similar to the approach explained in chapter 2. All you need to do is to add a data function to your test class:

 class TestGui: public QObject
 {
     Q_OBJECT

 private slots:
     void testGui_data();
     void testGui();
 };

Writing the Data Function

As before, a test function's associated data function carries the same name, appended by _data.

 void TestGui::testGui_data()
 {
     QTest::addColumn<QTestEventList>("events");
     QTest::addColumn<QString>("expected");

     QTestEventList list1;
     list1.addKeyClick('a');
     QTest::newRow("char") << list1 << "a";

     QTestEventList list2;
     list2.addKeyClick('a');
     list2.addKeyClick(Qt::Key_Backspace);
     QTest::newRow("there and back again") << list2 << "";
 }

First, we define the elements of the table using the QTest::addColumn() function: A list of GUI events, and the expected result of applying the list of events on a QWidget. Note that the type of the first element is QTestEventList.

A QTestEventList can be populated with GUI events that can be stored as test data for later usage, or be replayed on any QWidget.

In our current data function, we create two QTestEventList elements. The first list consists of a single click to the 'a' key. We add the event to the list using the QTestEventList::addKeyClick() function. Then we use the QTest::newRow() function to give the data set a name, and stream the event list and the expected result into the table.

The second list consists of two key clicks: an 'a' with a following 'backspace'. Again we use the QTestEventList::addKeyClick() to add the events to the list, and QTest::newRow() to put the event list and the expected result into the table with an associated name.

Rewriting the Test Function

Our test can now be rewritten:

 void TestGui::testGui()
 {
     QFETCH(QTestEventList, events);
     QFETCH(QString, expected);

     QLineEdit lineEdit;

     events.simulate(&lineEdit);

     QCOMPARE(lineEdit.text(), expected);
 }

The TestGui::testGui() function will be executed two times, once for each entry in the test data that we created in the associated TestGui::testGui_data() function.

First, we fetch the two elements of the data set using the QFETCH() macro. QFETCH() takes two arguments: the data type of the element and the element name. Then we create a QLineEdit, and apply the list of events on that widget using the QTestEventList::simulate() function.

Finally, we use the QCOMPARE() macro to check if the line edit's text is as expected.

As before, to make our test case a stand-alone executable, the following two lines are needed:

 QTEST_MAIN(TestGui)
 #include "testgui.moc"

The QTEST_MAIN() macro expands to a simple main() method that runs all the test functions, and since both the declaration and the implementation of our test class are in a .cpp file, we also need to include the generated moc file to make Qt's introspection work.

Example project @ code.qt.io