diff --git a/geometry/graham_scan_algorithm.cpp b/geometry/graham_scan_algorithm.cpp
index 80d5e3799..426751e85 100644
--- a/geometry/graham_scan_algorithm.cpp
+++ b/geometry/graham_scan_algorithm.cpp
@@ -74,6 +74,6 @@ void test() {
  * @returns 0 on exit
  *******************************************************************************/
 int main() {
-    test();
+    test();  // run self-test implementations
     return 0;
 }