First integration test

test/integration/templates/using-adder/lists.in.cmake

@@ -0,0 +1,11 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+project(using-adder)
+
+include("%{cpm_path}")
+
+%{packages}
+
+add_executable(using-adder using-adder.cpp)
+
+target_link_libraries(using-adder adder)

test/integration/templates/using-adder/using-adder.cpp

@@ -0,0 +1,9 @@
+#include <adder/adder.hpp>
+#include <cstdio>
+
+int main()
+{
+    int sum = adder::add(5, 3);
+    std::printf("%d\n", sum);
+    return 0;
+}