CTest checking that internet works before tests requiring internet

CMakeLists.txt

cmake_minimum_required(VERSION 3.19)

project(Connect LANGUAGES NONE)

enable_testing()

add_test(NAME InternetConnection COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_LIST_DIR}/connection.cmake)
set_property(TEST InternetConnection PROPERTY FIXTURES_SETUP InternetOK)

add_test(NAME NeedsInternet COMMAND ...)
set_property(TEST NeedsInternet PROPERTY FIXTURES_REQUIRED InternetOK)

connection.cmake

file(DOWNLOAD https://connectivitycheck.gstatic.com/generate_204
STATUS ret
TLS_VERIFY ON
)

list(GET ret 0 status)

if(NOT status EQUAL 0)
  list(GET ret 1 msg)
  message(FATAL_ERROR "Internet connectivity test failed.
  Return code: ${status}
  Error: ${msg}"
  )
endif()