qttestlib-manual.qdoc

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// Copyright (C) 2022 The Qt Company Ltd.
// Copyright (C) 2016 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
    \page qtest-overview.html
    \title Qt Test Overview
    \brief Overview of the Qt unit testing framework.
 
    \ingroup frameworks-technologies
    \ingroup qt-basic-concepts
 
    \keyword qtestlib
 
    Qt Test is a framework for unit testing Qt based applications and libraries.
    Qt Test provides
    all the functionality commonly found in unit testing frameworks as
    well as extensions for testing graphical user interfaces.
 
    Qt Test is designed to ease the writing of unit tests for Qt
    based applications and libraries:
 
    \table
    \header \li Feature \li Details
    \row
        \li \b Lightweight
        \li Qt Test consists of about 6000 lines of code and 60
           exported symbols.
    \row
        \li \b Self-contained
        \li Qt Test requires only a few symbols from the Qt Core module
           for non-gui testing.
    \row
        \li \b {Rapid testing}
        \li Qt Test needs no special test-runners; no special
           registration for tests.
    \row
        \li \b {Data-driven testing}
        \li A test can be executed multiple times with different test data.
    \row
        \li \b {Basic GUI testing}
        \li Qt Test offers functionality for mouse and keyboard simulation.
    \row
        \li \b {Benchmarking}
        \li Qt Test supports benchmarking and provides several measurement back-ends.
    \row
         \li \b {IDE friendly}
         \li Qt Test outputs messages that can be interpreted by Qt Creator, Visual
            Studio, and KDevelop.
    \row
         \li \b Thread-safety
         \li The error reporting is thread safe and atomic.
    \row
         \li \b Type-safety
         \li Extensive use of templates prevent errors introduced by
            implicit type casting.
    \row
         \li \b {Easily extendable}
         \li Custom types can easily be added to the test data and test output.
    \endtable
 
    You can use a Qt Creator wizard to create a project that contains Qt tests
    and build and run them directly from Qt Creator. For more information, see
    \l {Qt Creator: Running Autotests}{Running Autotests}.
 
    \section1 Creating a Test
 
    To create a test, subclass QObject and add one or more private slots to it. Each
    private slot is a test function in your test. QTest::qExec() can be used to execute
    all test functions in the test object.
 
    In addition, you can define the following private slots that are \e not
    treated as test functions. When present, they will be executed by the
    testing framework and can be used to initialize and clean up either the
    entire test or the current test function.
 
    \list
    \li \c{initTestCase()} will be called before the first test function is executed.
    \li \c{initTestCase_data()} will be called to create a global test data table.
    \li \c{cleanupTestCase()} will be called after the last test function was executed.
    \li \c{init()} will be called before each test function is executed.
    \li \c{cleanup()} will be called after every test function.
    \endlist
 
    Use \c initTestCase() for preparing the test. Every test should leave the
    system in a usable state, so it can be run repeatedly. Cleanup operations
    should be handled in \c cleanupTestCase(), so they get run even if the test
    fails.
 
    Use \c init() for preparing a test function. Every test function should
    leave the system in a usable state, so it can be run repeatedly. Cleanup
    operations should be handled in \c cleanup(), so they get run even if the
    test function fails and exits early.
 
    Alternatively, you can use RAII (resource acquisition is initialization),
    with cleanup operations called in destructors, to ensure they happen when
    the test function returns and the object moves out of scope.
 
    If \c{initTestCase()} fails, no test function will be executed. If \c{init()} fails,
    the following test function will not be executed, the test will proceed to the next
    test function.
 
    Example:
    \snippet code/doc_src_qtestlib.cpp 0
 
    Finally, if the test class has a static public \c{void initMain()} method,
    it is called by the QTEST_MAIN macros before the QApplication object
    is instantiated. This was added in 5.14.
 
    For more examples, refer to the \l{Qt Test Tutorial}.
 
    \section1 Increasing Test Function Timeout
 
    QtTest limits the run-time of each test to catch infinite loops and similar
    bugs. By default, any test function call will be interrupted after five
    minutes. For data-driven tests, this applies to each call with a distinct
    data-tag. This timeout can be configured by setting the \c QTEST_FUNCTION_TIMEOUT
    environment variable to the maximum number of milliseconds that is acceptable
    for a single call to take. If a test takes longer than the configured timeout,
    it is interrupted, and \c qFatal() is called. As a result, the test aborts by
    default, as if it had crashed.
 
    To set \c QTEST_FUNCTION_TIMEOUT from the command line on Linux or macOS, enter:
 
    \badcode
    QTEST_FUNCTION_TIMEOUT=900000
    export QTEST_FUNCTION_TIMEOUT
    \endcode
 
    On Windows:
    \badcode
    SET QTEST_FUNCTION_TIMEOUT=900000
    \endcode
 
    Then run the test inside this environment.
 
    Alternatively, you can set the environment variable programmatically in the
    test code itself, for example by calling, from the
    \l{Creating a Test}{initMain()} special method of your test class:
 
    \badcode
    qputenv("QTEST_FUNCTION_TIMEOUT", "900000");
    \endcode
 
    To calculate a suitable value for the timeout, see how long the test usually
    takes and decide how much longer it can take without that being a symptom of
    some problem. Convert that longer time to milliseconds to get the timeout value.
    For example, if you decide that a test that takes several minutes could
    reasonably take up to twenty minutes, for example on a slow machine,
    multiply \c{20 * 60 * 1000 = 1200000} and set the environment variable to
    \c 1200000 instead of the \c 900000 above.
 
    \if !defined(qtforpython)
    \section1 Building a Test
 
    You can build an executable that contains one test class that typically
    tests one class of production code. However, usually you would want to
    test several classes in a project by running one command.
 
    See \l {Chapter 1: Writing a Unit Test}{Writing a Unit Test} for a step by
    step explanation.
 
    \section2 Building with CMake and CTest
 
    You can use \l {Building with CMake and CTest} to create a test.
    \l{https://cmake.org/cmake/help/latest/manual/ctest.1.html}{CTest} enables
    you to include or exclude tests based on a regular expression that is
    matched against the test name. You can further apply the \c LABELS property
    to a test and CTest can then include or exclude tests based on those labels.
    All labeled targets will be run when \c {test} target is called on the
    command line.
 
    \note On Android, if you have one connected device or emulator, tests will
    run on that device. If you have more than one device connected, set the
    environment variable \c {ANDROID_DEVICE_SERIAL} to the
    \l {Android: Query for devices}{ADB serial number} of the device that
    you want to run tests on.
 
    There are several other advantages with CMake. For example, the result of
    a test run can be published on a web server using CDash with virtually no
    effort.
 
    CTest scales to very different unit test frameworks, and works out of the
    box with QTest.
 
    The following is an example of a CMakeLists.txt file that specifies the
    project name and the language used (here, \e mytest and C++), the Qt
    modules required for building the test (Qt5Test), and the files that are
    included in the test (\e tst_mytest.cpp).
 
    \quotefile code/doc_src_cmakelists.txt
 
    For more information about the options you have, see \l {Build with CMake}.
 
    \section2 Building with qmake
 
    If you are using \c qmake as your build tool, just add the
    following to your project file:
 
    \snippet code/doc_src_qtestlib.pro 1
 
    If you would like to run the test via \c{make check}, add the
    additional line:
 
    \snippet code/doc_src_qtestlib.pro 2
 
    To prevent the test from being installed to your target, add the
    additional line:
 
    \snippet code/doc_src_qtestlib.pro 3
 
    See the \l{Building a Testcase}{qmake manual} for
    more information about \c{make check}.
 
    \section2 Building with Other Tools
 
    If you are using other build tools, make sure that you add the location
    of the Qt Test header files to your include path (usually \c{include/QtTest}
    under your Qt installation directory). If you are using a release build
    of Qt, link your test to the \c QtTest library. For debug builds, use
    \c{QtTest_debug}.
 
    \endif
 
    \section1 Qt Test Command Line Arguments
 
    \section2 Syntax
 
    The syntax to execute an autotest takes the following simple form:
 
    \snippet code/doc_src_qtestlib.qdoc 2
 
    Substitute \c testname with the name of your executable. \c
    testfunctions can contain names of test functions to be
    executed. If no \c testfunctions are passed, all tests are run. If you
    append the name of an entry in \c testdata, the test function will be
    run only with that test data.
 
    For example:
 
    \snippet code/doc_src_qtestlib.qdoc 3
 
    Runs the test function called \c toUpper with all available test data.
 
    \snippet code/doc_src_qtestlib.qdoc 4
 
    Runs the \c toUpper test function with all available test data,
    and the \c toInt test function with the test data row called \c
    zero (if the specified test data doesn't exist, the associated test
    will fail and the available data tags are reported).
 
    \snippet code/doc_src_qtestlib.qdoc 5
 
    Runs the \c testMyWidget function test, outputs every signal
    emission and waits 500 milliseconds after each simulated
    mouse/keyboard event.
 
    \section2 Options
 
    \section3 Logging Options
 
    The following command line options determine how test results are reported:
 
    \list
    \li \c -o \e{filename,format} \br
    Writes output to the specified file, in the specified format (one
    of \c txt, \c csv, \c junitxml, \c xml, \c lightxml, \c teamcity
    or \c tap).  Use the special filename \c{-} (hyphen) to log to
    standard output.
    \li \c -o \e filename \br
    Writes output to the specified file.
    \li \c -txt \br
    Outputs results in plain text.
    \li \c -csv \br
    Outputs results as comma-separated values (CSV) suitable for
    import into spreadsheets. This mode is only suitable for
    benchmarks, since it suppresses normal pass/fail messages.
    \li \c -junitxml \br
    Outputs results as a \l{JUnit XML} document.
    \li \c -xml \br
    Outputs results as an XML document.
    \li \c -lightxml \br
    Outputs results as a stream of XML tags.
    \li \c -teamcity \br
    Outputs results in \l{TeamCity} format.
    \li \c -tap \br
    Outputs results in \l{Test Anything Protocol} (TAP) format.
    \endlist
 
    The first version of the \c -o option may be repeated in order to log
    test results in multiple formats, but no more than one instance of this
    option can log test results to standard output.
 
    If the first version of the \c -o option is used, neither the second version
    of the \c -o option nor the \c -txt, \c -xml, \c -lightxml, \c -teamcity,
    \c -junitxml or \c -tap options should be used.
 
    If neither version of the \c -o option is used, test results will be logged to
    standard output.  If no format option is used, test results will be logged in
    plain text.
 
    \section3 Test Log Detail Options
 
    The following command line options control how much detail is reported
    in test logs:
 
    \list
    \li \c -silent \br
    Silent output; only shows fatal errors, test failures and minimal status
    messages.
    \li \c -v1 \br
    Verbose output; shows when each test function is entered.
    (This option only affects plain text output.)
    \li \c -v2 \br
    Extended verbose output; shows each \l QCOMPARE() and \l QVERIFY().
    (This option affects all output formats and implies \c -v1 for plain text output.)
    \li \c -vs \br
    Shows all signals that get emitted and the slot invocations resulting from
    those signals.
    (This option affects all output formats.)
    \endlist
 
    \section3 Testing Options
 
    The following command-line options influence how tests are run:
 
    \list
    \li \c -functions \br
    Outputs all test functions available in the test, then quits.
    \li \c -datatags \br
    Outputs all data tags available in the test.
    A global data tag is preceded by ' __global__ '.
    \li \c -eventdelay \e ms \br
    If no delay is specified for keyboard or mouse simulation
    (\l QTest::keyClick(),
    \l QTest::mouseClick() etc.), the value from this parameter
    (in milliseconds) is substituted.
    \li \c -keydelay \e ms \br
    Like -eventdelay, but only influences keyboard simulation and not mouse
    simulation.
    \li \c -mousedelay \e ms \br
    Like -eventdelay, but only influences mouse simulation and not keyboard
    simulation.
    \li \c -maxwarnings \e number \br
    Sets the maximum number of warnings to output. 0 for unlimited, defaults to
    2000.
    \li \c -nocrashhandler \br
    Disables the crash handler on Unix platforms.
    On Windows, it re-enables the Windows Error Reporting dialog, which is
    turned off by default. This is useful for debugging crashes.
    \li \c -repeat \e n \br
    Run the testsuite n times or until the test fails. Useful for finding
    flaky tests. If negative, the tests are repeated forever. This is intended
    as a developer tool, and is only supported with the plain text logger.
    \li \c -skipblacklisted \br
    Skip the blacklisted tests. This option is intended to allow more accurate
    measurement of test coverage by preventing blacklisted tests from inflating
    coverage statistics. When not measuring test coverage, it is recommended to
    execute blacklisted tests to reveal any changes in their results, such as
    a new crash or the issue that caused blacklisting being resolved.
 
    \li \c -platform \e name \br
    This command line argument applies to all Qt applications, but might be
    especially useful in the context of auto-testing. By using the "offscreen"
    platform plugin (-platform offscreen) it's possible to have tests that use
    QWidget or QWindow run without showing anything on the screen. Currently
    the offscreen platform plugin is only fully supported on X11.
    \endlist
 
    \section3 Benchmarking Options
 
    The following command line options control benchmark testing:
 
    \list
    \li \c -callgrind \br
    Uses Callgrind to time benchmarks (Linux only).
    \li \c -tickcounter \br
    Uses CPU tick counters to time benchmarks.
    \li \c -eventcounter \br
    Counts events received during benchmarks.
    \li \c -minimumvalue \e n \br
    Sets the minimum acceptable measurement value.
    \li \c -minimumtotal \e n \br
    Sets the minimum acceptable total for repeated executions of a test function.
    \li \c -iterations \e n \br
    Sets the number of accumulation iterations.
    \li \c -median \e n \br
    Sets the number of median iterations.
    \li \c -vb \br
    Outputs verbose benchmarking information.
    \endlist
 
    \section3 Miscellaneous Options
 
    \list
    \li \c -help \br
    Outputs the possible command line arguments and gives some useful help.
    \endlist
 
    \section1 Qt Test Environment Variables
 
    You can set certain environment variables in order to affect
    the execution of an autotest:
 
    \list
    \li \c QTEST_DISABLE_CORE_DUMP \br
    Setting this variable to a non-zero value will disable the generation
    of a core dump file.
    \li \c QTEST_DISABLE_STACK_DUMP \br
    Setting this variable to a non-zero value will prevent Qt Test from
    printing a stacktrace in case an autotest times out or crashes.
    \li \c QTEST_FATAL_FAIL \br
    Setting this variable to a non-zero value will cause a failure in
    an autotest to immediately abort the entire autotest. This is useful
    to e.g. debug an unstable or intermittent failure in a test, by
    launching the test in a debugger. Support for this variable was
    added in Qt 6.1.
    \li \c QTEST_THROW_ON_FAIL (since 6.8) \br
    Setting this variable to a non-zero value will cause QCOMPARE()/QVERIFY()
    etc to throw on failure (as opposed to just returning from the
    immediately-surrounding function scope).
    \li \c QTEST_THROW_ON_SKIP (since 6.8) \br
    Same as \c QTEST_THROW_ON_FAIL, except affecting QSKIP().
    \endlist
 
    \section1 Creating a Benchmark
 
    To create a benchmark, follow the instructions for creating a test and then add a
    \l QBENCHMARK macro or \l QTest::setBenchmarkResult() to the test function that
    you want to benchmark. In the following code snippet, the macro is used:
 
    \snippet code/doc_src_qtestlib.cpp 12
 
    A test function that measures performance should contain either a single
    \c QBENCHMARK macro or a single call to \c setBenchmarkResult(). Multiple
    occurrences make no sense, because only one performance result can be
    reported per test function, or per data tag in a data-driven setup.
 
    Avoid changing the test code that forms (or influences) the body of a
    \c QBENCHMARK macro, or the test code that computes the value passed to
    \c setBenchmarkResult(). Differences in successive performance results
    should ideally be caused only by changes to the product you are testing.
    Changes to the test code can potentially result in misleading report of
    a change in performance. If you do need to change the test code, make
    that clear in the commit message.
 
    In a performance test function, the \c QBENCHMARK or \c setBenchmarkResult()
    should be followed by a verification step using \l QCOMPARE(), \l QVERIFY(),
    and so on. You can then flag a performance result as \e invalid if another
    code path than the intended one was measured. A performance analysis tool
    can use this information to filter out invalid results.
    For example, an unexpected error condition will typically cause the program
    to bail out prematurely from the normal program execution, and thus falsely
    show a dramatic performance increase.
 
    \section2 Selecting the Measurement Back-end
 
    The code inside the QBENCHMARK macro will be measured, and possibly also repeated
    several times in order to get an accurate measurement. This depends on the selected
    measurement back-end. Several back-ends are available. They can be selected on the
    command line:
 
    \target testlib-benchmarking-measurement
 
    \table
    \header \li Name
         \li Command-line Argument
         \li Availability
    \row \li Walltime
         \li (default)
         \li All platforms
    \row \li CPU tick counter
         \li -tickcounter
         \li Windows, \macos, Linux, many UNIX-like systems.
    \row \li Event Counter
         \li -eventcounter
         \li All platforms
    \row \li Valgrind Callgrind
         \li -callgrind
         \li Linux (if installed)
    \row \li Linux Perf
         \li -perf
         \li Linux
    \endtable
 
    In short, walltime is always available but requires many repetitions to
    get a useful result.
    Tick counters are usually available and can provide
    results with fewer repetitions, but can be susceptible to CPU frequency
    scaling issues.
    Valgrind provides exact results, but does not take
    I/O waits into account, and is only available on a limited number of
    platforms.
    Event counting is available on all platforms and it provides the number of events
    that were received by the event loop before they are sent to their corresponding
    targets (this might include non-Qt events).
 
    The Linux Performance Monitoring solution is available only on Linux and
    provides many different counters, which can be selected by passing an
    additional option \c {-perfcounter countername}, such as \c {-perfcounter
    cache-misses}, \c {-perfcounter branch-misses}, or \c {-perfcounter
    l1d-load-misses}. The default counter is \c {cpu-cycles}. The full list of
    counters can be obtained by running any benchmark executable with the
    option \c -perfcounterlist.
 
    \note
    \list
    \li Using the performance counter may require enabling access to non-privileged
        applications.
    \li Devices that do not support high-resolution timers default to
        one-millisecond granularity.
    \endlist
 
    See \l {Chapter 5: Writing a Benchmark}{Writing a Benchmark} in the Qt Test
    Tutorial for more benchmarking examples.
 
    \section1 Using Global Test Data
 
    You can define \c{initTestCase_data()} to set up a global test data table.
    Each test is run once for each row in the global test data table. When the
    test function itself \l{Chapter 2: Data Driven Testing}{is data-driven},
    it is run for each local data row, for each global data row. So, if there
    are \c g rows in the global data table and \c d rows in the test's own
    data-table, the number of runs of this test is \c g times \c d.
 
    Global data is fetched from the table using the \l QFETCH_GLOBAL() macro.
 
    The following are typical use cases for global test data:
 
    \list
        \li Selecting among the available database backends in QSql tests to run
            every test against every database.
        \li Doing all networking tests with and without SSL (HTTP versus HTTPS)
            and proxying.
        \li Testing a timer with a high precision clock and with a coarse one.
        \li Selecting whether a parser shall read from a QByteArray or from a
            QIODevice.
    \endlist
 
    For example, to test each number provided by \c {roundTripInt_data()} with
    each locale provided by \c {initTestCase_data()}:
 
    \snippet code/src_qtestlib_qtestcase_snippet.cpp 31
 
    On the command-line of a test you can pass the name of a function (with no
    test-class-name prefix) to run only that one function's tests. If the test
    class has global data, or the function is data-driven, you can append a data
    tag, after a colon, to run only that tag's data-set for the function. To
    specify both a global tag and a tag specific to the test function, combine
    them with a colon between, putting the global data tag first. For example
 
    \snippet code/doc_src_qtestlib.qdoc 6
 
    will run the \c zero test-case of the \c roundTripInt() test above (assuming
    its \c TestQLocale class has been compiled to an executable \c testqlocale)
    in each of the locales specified by \c initTestCase_data(), while
 
    \snippet code/doc_src_qtestlib.qdoc 7
 
    will run all three test-cases of \c roundTripInt() only in the C locale and
 
    \snippet code/doc_src_qtestlib.qdoc 8
 
    will only run the \c zero test-case in the C locale.
 
    Providing such fine-grained control over which tests are to be run can make
    it considerably easier to debug a problem, as you only need to step through
    the one test-case that has been seen to fail.
 
*/
 
/*!
    \page qtest-tutorial.html
    \brief A short introduction to testing with Qt Test.
    \nextpage {Chapter 1: Writing a Unit Test}{Chapter 1}
    \ingroup best-practices
 
    \title Qt Test Tutorial
 
    This tutorial introduces some of the features of the Qt Test framework. It
    is divided into six chapters:
 
    \list 1
    \li \l {Chapter 1: Writing a Unit Test}{Writing a Unit Test}
    \li \l {Chapter 2: Data Driven Testing}{Data Driven Testing}
    \li \l {Chapter 3: Simulating GUI Events}{Simulating GUI Events}
    \li \l {Chapter 4: Replaying GUI Events}{Replaying GUI Events}
    \li \l {Chapter 5: Writing a Benchmark}{Writing a Benchmark}
    \li \l {Chapter 6: Skipping Tests with QSKIP}{Skipping Tests}
    \endlist
 
 
*/