diff --git a/.gitignore b/.gitignore
index 7aabc6b..33c36d8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 i
 s
 t
+a.out
 .clangd
diff --git a/sum.cpp b/sum.cpp
index 052f808..f6de3e0 100644
--- a/sum.cpp
+++ b/sum.cpp
@@ -1,7 +1,14 @@
-#include <iostream>
+#include <cassert>
 
 template <typename T> auto sum(T final) { return final; }
 template <typename T, typename... Ts> auto sum(T first, Ts... rem) {
   return first + sum<Ts...>(rem...);
 }
-int main(void) { std::cout << sum<double, int, int, int>(1.5, 2, 3, 10); }
+int main(void) {
+  bool dummy = sum<double, int, int, int>(1.5, 2, 3, 10) == 16.5;
+  assert(dummy);
+  dummy = sum<int, int, int, int, int, int, int>(1, 5, 7, 8, 2, 3, 4) == 30;
+  assert(dummy);
+  dummy = sum<double>(1.5, 1, 2, 3.5) == 8.0;
+  assert(dummy);
+}