diff --git a/approximate-pi.c b/approximate-pi.c
index 6742590..cff7d98 100644
--- a/approximate-pi.c
+++ b/approximate-pi.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <stdio.h>
 #include <stdbool.h>
 
@@ -19,7 +20,12 @@ double approximate_pi(unsigned int steps) {
 
 int main(int argc, char *argv[]) {
   // printf("sizeof(int) = %d\n", sizeof(int));
-  printf("pi = %8.7f\n", approximate_pi(10000000));
+
+  double mypi = approximate_pi(100000000);
+
+  printf("pi = %8.7f\n", mypi);
+  assert(mypi > 3.141);
+  assert(mypi < 3.142);
 
   return 0;
 }