Doc: Describe initTestCase_data() function and QFETCH_GLOBAL macro

Fixes: QTBUG-24342
Change-Id: I8f8f3726c5d31e34af9bfe054572c08fc07e01e0
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/testlib/doc/snippets/code/src_qtestlib_qtestcase.cpp

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -296,3 +296,31 @@ QTest::keyClick(myWindow, Qt::Key_Escape, Qt::ShiftModifier, 200);
 
 }
 
+//! [30]
+void TestQLocale::initTestCase_data()
+{
+    QTest::addColumn<QLocale>("locale");
+    QTest::newRow("C") << QLocale::c();
+    QTest::newRow("UKish") << QLocale("en_GB");
+    QTest::newRow("USAish") << QLocale(QLocale::English);
+}
+
+void TestQLocale::roundTripInt_data()
+{
+    QTest::addColumn<int>("number");
+    QTest::newRow("one") << 1;
+    QTest::newRow("two") << 2;
+    QTest::newRow("ten") << 10;
+}
+//! [30]
+
+//! [31]
+void TestQLocale::roundTripInt()
+{
+    QFETCH_GLOBAL(QLocale, locale);
+    QFETCH(int, number);
+    bool ok;
+    QCOMPARE(locale.toInt(locale.toString(number), &ok), number);
+    QVERIFY(ok);
+}
+//! [31]

src/testlib/doc/src/qttestlib-manual.qdoc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Copyright (C) 2016 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
@@ -89,12 +89,14 @@
     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, there are four private slots that are \e not treated as test functions.
-    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.
+    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.
@@ -365,6 +367,34 @@
 
     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.cpp 31
 */
 
 /*!
@@ -508,10 +538,9 @@
     QTest::newRow() function. Each set of data will become a
     separate row in the test table.
 
-    \l QTest::newRow() takes one argument: a name that will be
-    associated with the data set. If the test fails, the name will be
-    used in the test log, referencing the failed data. Then we
-    stream the data set into the new table row. First an arbitrary
+    \l QTest::newRow() takes one argument: a name that will be associated
+    with the data set and used in the test log to identify the data set.
+    Then we stream the data set into the new table row. First an arbitrary
     string, and then the expected result of applying the
     QString::toUpper() function to that string.
 
@@ -543,6 +572,10 @@
         \li HELLO
     \endtable
 
+    When data is streamed into the row, each datum is asserted to match
+    the type of the column whose value it supplies. If any assertion fails,
+    the test is aborted.
+
     \section1 Rewriting the Test Function
 
     Our test function can now be rewritten:

src/testlib/qtestcase.qdoc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -220,8 +220,8 @@
    \relates QTest
 
    The fetch macro creates a local variable named \a name with the type \a type
-   on the stack. \a name has to match the element name from the test's data.
-   If no such element exists, the test will assert.
+   on the stack. The \a name and \a type must match a column from the test's
+   data table. This is asserted and the test will abort if the assertion fails.
 
    Assuming a test has the following data:
 
@@ -239,6 +239,33 @@
    by the test framework. The test function must have a _data function.
 */
 
+/*! \macro QFETCH_GLOBAL(type, name)
+
+   \relates QTest
+
+   This macro fetches a variable named \a name with the type \a type from
+   a row in the global data table. The \a name and \a type must match a
+   column in the global data table. This is asserted and the test will abort
+   if the assertion fails.
+
+   Assuming a test has the following data:
+
+   \snippet code/src_qtestlib_qtestcase.cpp 30
+
+   The test's own data is a single number per row. In this case,
+   \c initTestCase_data() also supplies a locale per row. Therefore,
+   this test will be run with every combination of locale from the
+   latter and number from the former.
+
+   \snippet code/src_qtestlib_qtestcase.cpp 31
+
+   The locale is read from the global data table using QFETCH_GLOBAL(),
+   and the number is read from the local data table using QFETCH().
+
+   \note This macro can only be used in test methods of a class with an
+   \c initTestCase_data() method.
+*/
+
 /*! \macro QWARN(message)
 
    \relates QTest