diff -Nur zxing-cpp-1.2.0/test/blackbox/CMakeLists.txt new/test/blackbox/CMakeLists.txt
--- zxing-cpp-1.2.0/test/blackbox/CMakeLists.txt	2021-05-28 12:47:09.000000000 +0200
+++ new/test/blackbox/CMakeLists.txt	2021-05-29 13:34:47.707152999 +0200
@@ -1,10 +1,13 @@
 cmake_minimum_required(VERSION 3.14)
 
-include(FetchContent)
-FetchContent_Declare (fmtlib
+find_package(fmt 7.1.2)
+if (NOT fmt_FOUND)
+    include(FetchContent)
+    FetchContent_Declare (fmtlib
         GIT_REPOSITORY https://github.com/fmtlib/fmt.git
         GIT_TAG 7.1.2)
-FetchContent_MakeAvailable (fmtlib) # Adds fmt::fmt
+    FetchContent_MakeAvailable (fmtlib) # Adds fmt::fmt
+endif()
 
 if (BUILD_READERS)
     add_executable (ReaderTest