diff --git a/Lts/DDS/DdsUnitTestsPlaceholder/ddsDataTopicTests_gtest.cpp b/Lts/DDS/DdsUnitTestsPlaceholder/ddsDataTopicTests_gtest.cpp
index bfc62e5f1..70d5d683f 100644
--- a/Lts/DDS/DdsUnitTestsPlaceholder/ddsDataTopicTests_gtest.cpp
+++ b/Lts/DDS/DdsUnitTestsPlaceholder/ddsDataTopicTests_gtest.cpp
@@ -1,7 +1,16 @@
 #include <gtest/gtest.h>
+#include "mocks/MockDDS.h"
 
 TEST(DataTopicSmokeGTest, Format) {
   char buf[64];
   snprintf(buf, sizeof(buf), "%d-%s", 42, "abc");
   EXPECT_STREQ(buf, "42-abc");
 }
+
+TEST(DataTopicSmokeGTest, MockDDSTopicFlow) {
+  MockDDS::clear_all();
+  MockDDS::publish("data/topic", "hello");
+  EXPECT_EQ(MockDDS::take_last("data/topic"), "hello");
+  MockDDS::publish("data/topic", "world");
+  EXPECT_EQ(MockDDS::take_last("data/topic"), "world");
+}
diff --git a/Lts/DDS/DdsUnitTestsPlaceholder/ddsFunctionTopicTests_gtest.cpp b/Lts/DDS/DdsUnitTestsPlaceholder/ddsFunctionTopicTests_gtest.cpp
index 5770ad2cb..c6cdf3f5f 100644
--- a/Lts/DDS/DdsUnitTestsPlaceholder/ddsFunctionTopicTests_gtest.cpp
+++ b/Lts/DDS/DdsUnitTestsPlaceholder/ddsFunctionTopicTests_gtest.cpp
@@ -1,4 +1,5 @@
 #include <gtest/gtest.h>
+#include "mocks/MockDDS.h"
 #include <map>
 
 TEST(FunctionTopicSmokeGTest, Containers) {
@@ -7,3 +8,10 @@ TEST(FunctionTopicSmokeGTest, Containers) {
   m["two"] = 2;
   EXPECT_EQ(m["two"], 2);
 }
+
+TEST(FunctionTopicSmokeGTest, MockDDSTopicAsSignal) {
+  MockDDS::clear_all();
+  MockDDS::publish("func/topic", "evt:1");
+  auto val = MockDDS::take_last("func/topic");
+  EXPECT_EQ(val, "evt:1");
+}
diff --git a/Lts/DDS/DdsUnitTestsPlaceholder/ddsGenericDataTests_gtest.cpp b/Lts/DDS/DdsUnitTestsPlaceholder/ddsGenericDataTests_gtest.cpp
index edba5cfff..591cea5d8 100644
--- a/Lts/DDS/DdsUnitTestsPlaceholder/ddsGenericDataTests_gtest.cpp
+++ b/Lts/DDS/DdsUnitTestsPlaceholder/ddsGenericDataTests_gtest.cpp
@@ -1,4 +1,5 @@
 #include <gtest/gtest.h>
+#include "mocks/MockDDS.h"
 
 TEST(GenericSmokeGTest, BasicStringOps) {
   std::string s = "MiXeD";
@@ -6,8 +7,9 @@ TEST(GenericSmokeGTest, BasicStringOps) {
   EXPECT_EQ(s, "mixed");
 }
 
-TEST(GenericSmokeGTest, VariantLike) {
-  // simulate basic core logic check
-  int v = 42;
-  EXPECT_EQ(v + 1, 43);
+TEST(GenericSmokeGTest, MockDDSPublishReceive) {
+  MockDDS::clear_all();
+  MockDDS::publish("topic1", "payload42");
+  auto r = MockDDS::take_last("topic1");
+  EXPECT_EQ(r, "payload42");
 }
diff --git a/Lts/DDS/DdsUnitTestsPlaceholder/mocks/MockDDS.cpp b/Lts/DDS/DdsUnitTestsPlaceholder/mocks/MockDDS.cpp
new file mode 100644
index 000000000..6e0d1cf55
--- /dev/null
+++ b/Lts/DDS/DdsUnitTestsPlaceholder/mocks/MockDDS.cpp
@@ -0,0 +1,27 @@
+#include "MockDDS.h"
+#include <map>
+#include <mutex>
+
+namespace MockDDS {
+
+static std::map<std::string, std::string> g_last_message;
+static std::mutex g_mtx;
+
+void publish(const std::string &topic, const std::string &msg) {
+    std::lock_guard<std::mutex> lk(g_mtx);
+    g_last_message[topic] = msg;
+}
+
+std::string take_last(const std::string &topic) {
+    std::lock_guard<std::mutex> lk(g_mtx);
+    auto it = g_last_message.find(topic);
+    if (it == g_last_message.end()) return std::string();
+    return it->second;
+}
+
+void clear_all() {
+    std::lock_guard<std::mutex> lk(g_mtx);
+    g_last_message.clear();
+}
+
+} // namespace MockDDS
diff --git a/Lts/DDS/DdsUnitTestsPlaceholder/mocks/MockDDS.h b/Lts/DDS/DdsUnitTestsPlaceholder/mocks/MockDDS.h
new file mode 100644
index 000000000..08e261b68
--- /dev/null
+++ b/Lts/DDS/DdsUnitTestsPlaceholder/mocks/MockDDS.h
@@ -0,0 +1,11 @@
+#pragma once
+#include <string>
+
+namespace MockDDS {
+
+// Very small mock: single-writer, single-last-message per topic store.
+void publish(const std::string &topic, const std::string &msg);
+std::string take_last(const std::string &topic);
+void clear_all();
+
+}