diff --git a/Makefile b/Makefile
index f2bc3a0..22568ce 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@ clean:
 distclean: clean
 	rm -Rf .gnupg .pEp_management*
 
-test: test_adapter
+test: test_adapter test_library
 ifeq ($(HOME),$(PREFIX))
 	-ln -fs $$HOME/lib
 endif
@@ -36,6 +36,9 @@ endif
 test_adapter: test_adapter.o $(TARGET)
 	$(CXX) -o $@ -L$(PEP)/lib -lpEpEngine -L. -lpEpAdapter $<
 
+test_library: test_library.o $(TARGET)
+	$(CXX) -o $@ -L$(PEP)/lib -lpEpEngine -L. -lpEpAdapter $<
+
 install: $(TARGET)
 	-mkdir -p $(PEP)/include
 	cp $(HEADERS) $(PEP)/include
diff --git a/test_library.cc b/test_library.cc
new file mode 100644
index 0000000..aa20382
--- /dev/null
+++ b/test_library.cc
@@ -0,0 +1,117 @@
+// small unittest program for libpEpAdapter
+// TODO: use Gtest or the like for more modular unit tests!
+
+#include "pc_container.hh"
+#include <cstdio>
+#include <cstdlib>
+#include <iostream>
+#include <thread>
+
+
+using namespace pEp;
+
+
+// Producer's data:
+class P
+{
+public:
+	P(int i)
+	: data{new char[64]}
+	{
+		snprintf(data, 63, "%i", i);
+	}
+	
+	P(const P&) = delete;
+	void operator=(const P&) = delete;
+	
+	~P()
+	{
+		std::cerr << "~P(): data=" << (data ? data : "(NULL)" ) << '\n';
+		delete[] data;
+	}
+	
+	char* data;
+};
+
+
+// Consumer's data:
+class C
+{
+public:
+	C(int _i) : i(_i) {}
+	int i;
+};
+
+pc_container<P,C> pc;
+
+void consumer_thread()
+{
+	bool keep_running = true;
+	int sum = 0;
+	while(keep_running)
+	{
+		auto q = pc.get_changed(); // might block, that is okay.
+		switch(q.state())
+		{
+			case PC_State::Created:
+			{
+				const int value = atoi( q.pdata->data );
+				if(value<0)
+				{
+					std::cerr << "Q\n";
+					keep_running = false;
+				}else{
+					std::cerr << "C";
+					q.cdata = new C( value );
+					sum += q.cdata->i;
+				}
+				break;
+			}
+			case PC_State::Deleted:
+			{
+				std::cerr << "D";
+				sum -= q.cdata->i;
+				delete q.cdata;
+				break;
+			}
+			case PC_State::Changed:
+			{
+				std::cerr << "X";
+				sum -= q.cdata->i;
+				delete q.cdata;
+				q.cdata = new C( atoi( q.pdata->data ) );
+				sum += q.cdata->i;
+				break;
+			}
+			default: throw "Illegal state";
+		}
+	}
+	
+	std::cout << "Consumer sum: " << sum << ".\n";
+}
+
+int main()
+{
+	for(int i=0; i<10; ++i)
+	{
+		pc.insert( new P(i) );
+	}
+	
+	std::thread t{ &consumer_thread };
+	
+	for(int i=10; i<100; ++i)
+	{
+		pc.insert( new P(i) );
+	}
+	
+	while( !pc.empty() )
+	{
+		auto q = pc.begin();
+		delete q->pdata;
+		pc.erase( q );
+	}
+	
+	pc.insert( new P(-1) );
+	
+	t.join();
+}