Handle multiple components: Add integration test

This adds integration test to verify whether DroneCore can
recognize different type of components. Below is the procedure
to test it.
1. Connect a camera to Linux system
2. Launch Camera streaming Daemon
3. Launch PX4 SITL
4. Run SitlTest.DiscoverOneAutopilotAndCamera test
The test discovers two componets (autopilot and camera).

core/device.cpp

@@ -167,9 +167,12 @@ void Device::process_heartbeat(const mavlink_message_t &message)
 
     /* If we don't know the UUID yet, we try to find out. */
     // Lets request autopilot version only from an Autopilot.
-    if (heartbeat.autopilot != MAV_AUTOPILOT_INVALID
-        && _target_uuid == 0
-        && !_target_uuid_initialized) {
+    if (heartbeat.autopilot == MAV_AUTOPILOT_INVALID &&
+        _target_uuid == 0 && !_target_uuid_initialized) {
+        // For Non-Autopilot components, lets fill UUID by ourself.
+        _target_uuid_initialized = true;
+        _target_uuid = message.sysid;
+    } else if (_target_uuid == 0 && !_target_uuid_initialized) {
         request_autopilot_version();
     }
 

integration_tests/CMakeLists.txt

@@ -15,6 +15,7 @@ add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} --verbose)
 # This includes all GTests that run integration tests
 add_executable(integration_tests_runner
     ../core/unittests_main.cpp
+    multi_component_discovery.cpp
     simple_connect.cpp
     async_connect.cpp
     telemetry_simple.cpp

integration_tests/multi_component_discovery.cpp

@@ -0,0 +1,32 @@
+#include <iostream>
+#include "integration_test_helper.h"
+#include "global_include.h"
+#include "dronecore.h"
+
+using namespace dronecore;
+using namespace std::chrono;
+using namespace std::this_thread;
+using namespace std::placeholders;
+static size_t _component_count = 0;
+
+static void on_component_discover(uint64_t uuid, uint8_t component_id)
+{
+    if (uuid && int(component_id)) {
+        _component_count++;
+    }
+    std::cout << "Discovered component " << int(component_id)
+              << " on vehicle " << uuid << std::endl;
+}
+
+TEST_F(SitlTest, DiscoverOneAutopilotAndCamera)
+{
+    DroneCore connection;
+    std::cout << "started" << std::endl;
+
+    connection.add_udp_connection();
+    connection.register_on_discover(std::bind(on_component_discover, _1, _2));
+
+    sleep_for(seconds(5));
+    EXPECT_EQ(_component_count, 2);
+    std::cout << "exiting" << std::endl;
+}