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Chapter 1: Writing a Unit Test

Files:

• tutorial1/testqstring.cpp

In this first chapter we will see how to write a simple unit test for a class, and how to execute it.

Writing a Test

Let's assume you want to test the behavior of our QString class. First, you need a class that contains your test functions. This class has to inherit from QObject:

    #include <QtTest>

    class TestQString: public QObject
    {
        Q_OBJECT
    private slots:
        void toUpper();
    };

Note that you need to include the QtTest namespace, and that the test function have to be declared as a private slot so the test framework finds it and can execute it.

Then you need to implement the test function itself. The implementation could look like this:

    void TestQString::toUpper()
    {
        QString str = "Hello";
        VERIFY(str.toUpper()== "HELLO");
    }

The VERIFY() macro evaluates the expression passed as its argument. If the expression evaluates to true, the execution of the test function continues. Otherwise, a message describing the failure is appended to the test log, and the test function stops executing.

But if you want a more verbose output to the test log, you should use the COMPARE() macro instead:

    void TestQString::toUpper()
    {
        QString str = "Hello";
        COMPARE(str.toUpper(), QString("HELLO"));
    }

If the strings are not equal, the contents of both strings is appended to the test log, making it immediately visible why the comparison failed.

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

    QTTEST_MAIN(TestQString)
    #include "testqstring.moc"

The QTTEST_MAIN() macro expands to a simple main() method that runs all the test functions. Note that if 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.

Executing a Test

Now that we finished writing our test, we want to execute it. Assuming that our test was saved as testqstring.cpp in an empty directory: we build the test using qmake to create a project and generate a makefile.

    /myTestDirectory$ qmake -project
    /myTestDirectory$ qmake
    /myTestDirectory$ make

Note:If you're using windows, replace make with nmake or whatever build tool you use.

Running the resulting executable should give you the following output:

    ********* Start testing of TestQString *********
    Config: Using QtTest library 2.0.0, Qt 4.0.1
    PASS   : TestQString::initTestCase()
    PASS   : TestQString::toUpper()
    PASS   : TestQString::cleanupTestCase()
    Totals: 3 passed, 0 failed, 0 skipped
    ********* Finished testing of TestQString *********

Congratulations! You just wrote and executed your first unit test using the QtTest framework.

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