Qt Quick auto test that shows the two potential points of failure when creating objects from QQmlComponent. Note that window.qml must go in a directory named "data".

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)

project(tst_untitled LANGUAGES CXX)

enable_testing()

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Gui Test Quick)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Gui Test Quick)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_executable(tst_untitled tst_untitled.cpp)
add_test(NAME tst_untitled COMMAND tst_untitled)

target_link_libraries(tst_untitled
    PRIVATE
        Qt${QT_VERSION_MAJOR}::Gui
        Qt${QT_VERSION_MAJOR}::Test
        Qt${QT_VERSION_MAJOR}::Quick
)

tst_untitled.cpp

#include <QtTest>
#include <QQmlEngine>
#include <QQmlComponent>
#include <QQuickWindow>
#include <memory>

class tst_untitled : public QObject
{
    Q_OBJECT

private slots:
    void testUniqueInstantiationError();
};

void tst_untitled::testUniqueInstantiationError()
{
    QQmlEngine engine;
    QQmlComponent component(&engine);
    component.loadUrl(QUrl::fromLocalFile(QFINDTESTDATA("data/window.qml")));
    QVERIFY2(component.isReady(), qPrintable(component.errorString()));

    // Attempt creation with missing initial properties to force instantiation failure.
    QVariantMap emptyProperties;
    std::unique_ptr<QObject> rootObject(component.createWithInitialProperties(emptyProperties));
    QVERIFY2(rootObject, qPrintable(component.errorString()));
}

QTEST_MAIN(tst_untitled)
#include "tst_untitled.moc"

window.qml

import QtQuick

Window {
    id: root

    // This compiles successfully (loadUrl passes),
    // but object instantiation will fail if this isn't supplied.
    required property string mandatoryConfiguration

    width: 640
    height: 480
    title: "Test Window"
}