Add EventQueue tests

unittest/vslib/Makefile.am

@@ -11,7 +11,8 @@ tests_SOURCES = main.cpp \
 				TestCorePortIndexMapContainer.cpp \
 				TestCorePortIndexMapFileParser.cpp \
 				TestEventPayloadNetLinkMsg.cpp \
-				TestEventPayloadPacket.cpp
+				TestEventPayloadPacket.cpp \
+				TestEventQueue.cpp
 
 tests_CXXFLAGS = $(DBGFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS_COMMON)
 tests_LDADD = $(LDADD_GTEST) $(top_srcdir)/vslib/libSaiVS.a -lhiredis -lswsscommon -lpthread -L$(top_srcdir)/meta/.libs -lsaimetadata -lsaimeta -lzmq $(CODE_COVERAGE_LIBS)

unittest/vslib/TestEventQueue.cpp

@@ -0,0 +1,25 @@
+#include "EventQueue.h"
+
+#include <linux/if.h>
+
+#include <gtest/gtest.h>
+
+using namespace saivs;
+
+TEST(EventQueue, ctr)
+{
+    EXPECT_THROW(std::make_shared<EventQueue>(nullptr), std::runtime_error);
+
+    auto s = std::make_shared<Signal>();
+
+    EventQueue eq(s);
+}
+
+TEST(EventQueue, size)
+{
+    auto s = std::make_shared<Signal>();
+
+    EventQueue eq(s);
+
+    EXPECT_EQ(eq.size(), 0);
+}

vslib/EventQueue.cpp

@@ -12,7 +12,10 @@ EventQueue::EventQueue(
 {
     SWSS_LOG_ENTER();
 
-    // empty
+    if (signal == nullptr)
+    {
+        SWSS_LOG_THROW("signal can't be nullptr");
+    }
 }
 
 void EventQueue::enqueue(