TestCase: add createTemporaryObject(), createTemporaryQmlObject()

A typical pattern with QML tests is to dynamically create
an item and then destroy it at the end of the test function:

TestCase {
    id: testCase
    name: "MyTest"
    when: windowShown

    function test_click() {
        var item = Qt.createQmlObject("import QtQuick 2.0; Item {}", testCase);
        verify(item);

        // Test item...

        item.destroy();
    }
}

The problem with this pattern is that any failures in the test function
will cause the call to item.destroy() to be skipped, leaving the item
hanging around in the scene until the test case has finished. This can
result in interference with future tests; for example, by blocking input
events or producing unrelated debug output that makes it difficult to
follow the code's execution.

By calling e.g. createTemporaryQmlObject() instead, the object is
guaranteed to be destroyed at the end of the test function:

TestCase {
    id: testCase
    name: "MyTest"
    when: windowShown

    function test_click() {
        var item = createTemporaryObject("import QtQuick 2.0; Item {}", testCase);
        verify(item);

        // Test item...

        // Don't need to worry about destroying "item" here.
    }
}

[ChangeLog][TestCase] Added createTemporaryObject() and
createTemporaryQmlObject() functions that can be used to ensure that
dynamically created objects are destroyed at the end of each test
function.

Change-Id: I483342052462aa86464c86bf2082892712dceb58
Task-number: QTBUG-56361
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Michael Brasser <michael.brasser@live.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/imports/testlib/qmldir b/src/imports/testlib/qmldir
index 9da8ebb4be..e5757f6a88 100644
--- a/src/imports/testlib/qmldir
+++ b/src/imports/testlib/qmldir
@@ -3,4 +3,5 @@ plugin qmltestplugin
 classname QTestQmlModule
 typeinfo plugins.qmltypes
 TestCase 1.0 TestCase.qml
+TestCase 1.2 TestCase.qml
 SignalSpy 1.0 SignalSpy.qml