tests: upgrade DDS smoke-tests to Qt Test-based checks (QString, QVariant, containers)

Lts/DDS/DdsUnitTestsPlaceholder/ddsGenericDataTests_smoke.cpp

@@ -1,5 +1,19 @@
-#include <iostream>
-int main() {
-  std::cout << "[smoke] ddsGenericDataTests_smoke running" << std::endl;
-  return 0;
-}
+#include <QObject>
+#include <QtTest>
+
+class GenericSmokeTest : public QObject {
+  Q_OBJECT
+private slots:
+  void test_string_ops() {
+    QString s = QString::fromUtf8("mIxEd");
+    QCOMPARE(s.toLower(), QString("mixed"));
+  }
+  void test_basic_qvariant() {
+    QVariant v = QString("value");
+    QVERIFY(v.canConvert<QString>());
+    QCOMPARE(v.toString(), QString("value"));
+  }
+};
+
+QTEST_MAIN(GenericSmokeTest)
+#include "ddsGenericDataTests_smoke.moc"