diff --git a/c-programming/math/opt_int_div.h b/c-programming/math/opt_int_div.h
index 71031b9..9ab511c 100644
--- a/c-programming/math/opt_int_div.h
+++ b/c-programming/math/opt_int_div.h
@@ -1,7 +1,7 @@
 /*
  * opt_int_div.h
  *
- * "Optimized integer division"
+ * "Optimized integer division": A header-only library
  *
  * Author: Intel A80486DX2-66
  * License: Creative Commons Zero 1.0 Universal
diff --git a/c-programming/math/opt_int_div.c b/c-programming/math/opt_int_div.test.c
similarity index 93%
rename from c-programming/math/opt_int_div.c
rename to c-programming/math/opt_int_div.test.c
index 4a8d603..238a096 100644
--- a/c-programming/math/opt_int_div.c
+++ b/c-programming/math/opt_int_div.test.c
@@ -9,9 +9,8 @@
 
 #include "opt_int_div.h"
 
-#ifdef TEST
-# include <inttypes.h>
-# include <stdio.h>
+#include <inttypes.h>
+#include <stdio.h>
 
 int main(void) {
 	printf("Loop: a > 0, b > 0\n");
@@ -43,4 +42,3 @@ int main(void) {
 
 	return 0;
 }
-#endif