message: includes CTest module resp. BUILD_TESTING option
diff: @@ -9,7 +9,7 @@ project(nlohmann_json VERSION 3.0.0 LANGUAGES CXX)
  ##
  ## OPTIONS
  ##
  -option(JSON_BuildTests "Build the unit tests" ON)
  +option(JSON_BuildTests "Build the unit tests when BUILD_TESTING is enabled." ON)
  ##
  ## CONFIGURATION
  @@ -54,7 +54,9 @@ endif()
  ## TESTS
  ## create and configure the unit test target
  ##
  -if(JSON_BuildTests)
  +include(CTest) #adds option BUILD_TESTING (default ON)
  +
  +if(BUILD_TESTING AND JSON_BuildTests)
  enable_testing()
  include_directories(${NLOHMANN_JSON_SOURCE_DIR})
  add_subdirectory(test)
  