diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 71bf957..135aa7f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,3 +1,13 @@
 cmake_minimum_required(VERSION 3.0)
 project(test)
+
+option(BUILD_TXT "build hello world txt file" OFF)
+
 add_executable(hello_world hello_world.cpp)
+
+if(BUILD_TXT)
+  add_custom_target(
+    hello_world_txt ALL
+    COMMAND echo "Hello world!" >> ${CMAKE_CURRENT_BINARY_DIR}/hello_world.txt
+  )
+endif()