Chapter 3: Simulating GUI Events

Qt Test features some mechanisms to test graphical user interfaces. Instead of simulating native window system events, Qt Test sends internal Qt events. That means there are no side-effects on the machine the tests are running on.

This chapter demonstrates how to write a simple GUI test.

Writing a GUI Test

This time, let's assume you want to test the behavior of our QLineEdit class. As before, you will need a class that contains your test function:

 #include <QtWidgets>
 #include <QTest>

 class TestGui: public QObject
 {
     Q_OBJECT

 private slots:
     void testGui();

 };

The only difference is that you need to include the Qt GUI class definitions in addition to the QTest namespace.

 void TestGui::testGui()
 {
     QLineEdit lineEdit;

     QTest::keyClicks(&lineEdit, "hello world");

     QCOMPARE(lineEdit.text(), QString("hello world"));
 }

In the implementation of the test function, we first create a QLineEdit. Then, we simulate writing "hello world" in the line edit using the QTest::keyClicks() function.

QTest::keyClicks() simulates clicking a sequence of keys on a widget. Optionally, a keyboard modifier can be specified as well as a delay (in milliseconds) of the test after each key click. In a similar way, you can use the QTest::keyClick(), QTest::keyPress(), QTest::keyRelease(), QTest::mouseClick(), QTest::mouseDClick(), QTest::mouseMove(), QTest::mousePress() and QTest::mouseRelease() functions to simulate the associated GUI events.

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

Preparing the Stand-Alone Executable

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.

Building the Executable

You can build the test case executable using CMake or qmake.

Building with CMake

Configure your build settings in your CMakeLists.txt file:

 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

 cmake_minimum_required(VERSION 3.16)
 project(tutorial3 LANGUAGES CXX)

 find_package(Qt6 REQUIRED COMPONENTS Core Gui Test Widgets)

 qt_standard_project_setup()

 qt_add_executable(tutorial3
     testgui.cpp
 )

 set_target_properties(tutorial3 PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )

 target_link_libraries(tutorial3 PRIVATE
     Qt6::Core
     Qt6::Gui
     Qt6::Test
     Qt6::Widgets
 )

 install(TARGETS tutorial3
     BUNDLE  DESTINATION .
     RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
     LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
 )

 qt_generate_deploy_app_script(
     TARGET tutorial3
     OUTPUT_SCRIPT deploy_script
     NO_UNSUPPORTED_PLATFORM_ERROR
 )
 install(SCRIPT ${deploy_script})

Next, from the command line, run either cmake or use the qt-cmake convenience script located in Qt-prefix/<version>/<platform>/bin/qt-cmake:

 <Qt-prefix>/<version>/<platform>/bin/qt-cmake <source-dir> <build-dir> -G Ninja

Then, run your preferred generator tool to build the executable. Here, we're using Ninja:

 ninja

Building with qmake

Configure your build settings in your .pro file:

 QT += widgets testlib

 SOURCES = testgui.cpp

 # install
 target.path = $$[QT_INSTALL_EXAMPLES]/qtestlib/tutorial3
 INSTALLS += target

Next, run qmake, and, finally, run make to build your executable:

 qmake
 make

Running the Executable

Running the resulting executable should give you the following output:

 ********* Start testing of TestGui *********
 Config: Using QtTest library %VERSION%, Qt %VERSION%
 PASS   : TestGui::initTestCase()
 PASS   : TestGui::testGui()
 PASS   : TestGui::cleanupTestCase()
 Totals: 3 passed, 0 failed, 0 skipped, 0 blacklisted, 20ms
 ********* Finished testing of TestGui **