diff --git a/entrypoint.sh b/entrypoint.sh
old mode 100755
new mode 100644
diff --git a/testdata/test.cpp b/testdata/test.cpp
index 308af3e..1bb4efc 100644
--- a/testdata/test.cpp
+++ b/testdata/test.cpp
@@ -1,5 +1,6 @@
 // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 //
+#include <atomic>
 #include "test.hpp"
 #include <iostream>
 
@@ -13,9 +14,24 @@ class Hoge
     int m_a;
 };
 
+// https://github.com/yohhoy/cpp-longest-identifier/wiki
+bool longest_identifier()
+{
+    std::atomic<int> x(3);
+
+    int expected = 3;
+    const bool result = std::atomic_compare_exchange_strong_explicit(&x, &expected, 2,
+                                                               std::memory_order_acquire,
+                                                               std::memory_order_acquire);
+
+    std::cout << std::boolalpha << result << " " << x.load() << " " << expected << std::endl;
+    return result;
+}
+
 int main(int, const char**)
 {
     Hoge hoge(42);
+    longest_identifier();
     std::cout << hoge.getA() << std::endl;
     return 0;
 }