Add a test for container API symmetry

Akin to the successful tst_QStringApiSymmetry, add such a test for
generic containers, too. Yes, we have tst_collections, but it's a
cut'n'paste mess that makes it hard to systematically perform
cross-class checks for consistency. This new test, still in its
infancy, uses templates and thus ensures that exactly the same checks
are run on all containers.

Starting out with front()/back(), which the string classes were found
to lack, we will build this test up, as we did and continue to do with
the string API one.

Change-Id: I07323340b5612ecc658232b2776d788018010d0d
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

tests/auto/corelib/tools/containerapisymmetry/.gitignore

@@ -0,0 +1 @@
+tst_containerapisymmetry

tests/auto/corelib/tools/containerapisymmetry/containerapisymmetry.pro

@@ -0,0 +1,7 @@
+CONFIG += testcase
+TARGET = tst_containerapisymmetry
+SOURCES  += tst_containerapisymmetry.cpp
+QT = core testlib
+
+# This test does not work with strict iterators
+DEFINES -= QT_STRICT_ITERATORS

tests/auto/corelib/tools/containerapisymmetry/tst_containerapisymmetry.cpp

@@ -0,0 +1,84 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest/QtTest>
+
+#include "qlinkedlist.h"
+#include "qlist.h"
+#include "qvarlengtharray.h"
+#include "qvector.h"
+
+#include <vector> // for reference
+
+class tst_ContainerApiSymmetry : public QObject
+{
+    Q_OBJECT
+
+private:
+    template <typename Container>
+    void front_back_impl() const;
+
+private Q_SLOTS:
+    void front_back_std_vector() { front_back_impl<std::vector<int>>(); }
+    void front_back_QVector() { front_back_impl<QVector<int>>(); }
+    void front_back_QList() { front_back_impl<QList<qintptr>>(); }
+    void front_back_QLinkedList() { front_back_impl<QLinkedList<int>>(); }
+    void front_back_QVarLengthArray() { front_back_impl<QVarLengthArray<int>>(); }
+};
+
+template <typename Container>
+Container make(int size)
+{
+    Container c;
+    int i = 1;
+    while (size--)
+        c.push_back(typename Container::value_type(i++));
+    return c;
+}
+
+template <typename T> T clean(T &&t) { return std::forward<T>(t); }
+
+template <typename Container>
+void tst_ContainerApiSymmetry::front_back_impl() const
+{
+    using V = typename Container::value_type;
+    auto c1 = make<Container>(1);
+    QCOMPARE(clean(c1.front()), V(1));
+    QCOMPARE(clean(c1.back()), V(1));
+    QCOMPARE(clean(qAsConst(c1).front()), V(1));
+    QCOMPARE(clean(qAsConst(c1).back()), V(1));
+
+    auto c2 = make<Container>(2);
+    QCOMPARE(clean(c2.front()), V(1));
+    QCOMPARE(clean(c2.back()), V(2));
+    QCOMPARE(clean(qAsConst(c2).front()), V(1));
+    QCOMPARE(clean(qAsConst(c2).back()), V(2));
+}
+
+QTEST_APPLESS_MAIN(tst_ContainerApiSymmetry)
+#include "tst_containerapisymmetry.moc"

tests/auto/corelib/tools/tools.pro

@@ -1,6 +1,7 @@
 TEMPLATE=subdirs
 SUBDIRS=\
     collections \
+    containerapisymmetry \
     qalgorithms \
     qarraydata \
     qarraydata_strictiterators \