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

Lts/DDS/DdsUnitTestsPlaceholder/ddsFunctionTopicTests_smoke.cpp

@@ -1,5 +1,22 @@
-#include <iostream>
-int main() {
-  std::cout << "[smoke] ddsFunctionTopicTests_smoke running" << std::endl;
-  return 0;
-}
+#include <QObject>
+#include <QtTest>
+
+class FunctionTopicSmokeTest : public QObject {
+  Q_OBJECT
+private slots:
+  void test_containers() {
+    QStringList list;
+    list << "a" << "b" << "c";
+    QCOMPARE(list.size(), 3);
+    QVERIFY(list.contains("b"));
+  }
+  void test_qmap_basic() {
+    QMap<QString,int> m;
+    m["one"] = 1;
+    m["two"] = 2;
+    QCOMPARE(m.value("two"), 2);
+  }
+};
+
+QTEST_MAIN(FunctionTopicSmokeTest)
+#include "ddsFunctionTopicTests_smoke.moc"