function(run_test ACTION INIT TARGET EXPECTED)
  cmake_diagnostic(SET CMD_AUTHOR ${INIT})

  cmake_diagnostic(GET CMD_AUTHOR action)
  if(NOT "${action}" STREQUAL "${INIT}")
    message(SEND_ERROR "failed to set diagnostic state")
  endif()

  cmake_diagnostic(${ACTION} CMD_AUTHOR ${TARGET})

  cmake_diagnostic(GET CMD_AUTHOR action)
  if(NOT "${action}" STREQUAL "${EXPECTED}")
    message(SEND_ERROR
      "failed to change diagnostic state"
      " (expected '${EXPECTED}', actual '${action}')"
    )
  endif()
endfunction()

run_test(SET IGNORE WARN WARN)
run_test(SET IGNORE SEND_ERROR SEND_ERROR)
run_test(SET IGNORE FATAL_ERROR FATAL_ERROR)

run_test(PROMOTE IGNORE IGNORE IGNORE)
run_test(PROMOTE IGNORE WARN WARN)
run_test(PROMOTE IGNORE SEND_ERROR SEND_ERROR)
run_test(PROMOTE IGNORE FATAL_ERROR FATAL_ERROR)

run_test(PROMOTE WARN IGNORE WARN)
run_test(PROMOTE WARN WARN WARN)
run_test(PROMOTE WARN SEND_ERROR SEND_ERROR)
run_test(PROMOTE WARN FATAL_ERROR FATAL_ERROR)

run_test(PROMOTE SEND_ERROR IGNORE SEND_ERROR)
run_test(PROMOTE SEND_ERROR WARN SEND_ERROR)
run_test(PROMOTE SEND_ERROR SEND_ERROR SEND_ERROR)
run_test(PROMOTE SEND_ERROR FATAL_ERROR FATAL_ERROR)

run_test(PROMOTE FATAL_ERROR IGNORE FATAL_ERROR)
run_test(PROMOTE FATAL_ERROR WARN FATAL_ERROR)
run_test(PROMOTE FATAL_ERROR SEND_ERROR FATAL_ERROR)
run_test(PROMOTE FATAL_ERROR FATAL_ERROR FATAL_ERROR)

run_test(DEMOTE IGNORE IGNORE IGNORE)
run_test(DEMOTE IGNORE WARN IGNORE)
run_test(DEMOTE IGNORE SEND_ERROR IGNORE)
run_test(DEMOTE IGNORE FATAL_ERROR IGNORE)

run_test(DEMOTE WARN IGNORE IGNORE)
run_test(DEMOTE WARN WARN WARN)
run_test(DEMOTE WARN SEND_ERROR WARN)
run_test(DEMOTE WARN FATAL_ERROR WARN)

run_test(DEMOTE SEND_ERROR IGNORE IGNORE)
run_test(DEMOTE SEND_ERROR WARN WARN)
run_test(DEMOTE SEND_ERROR SEND_ERROR SEND_ERROR)
run_test(DEMOTE SEND_ERROR FATAL_ERROR SEND_ERROR)

run_test(DEMOTE FATAL_ERROR IGNORE IGNORE)
run_test(DEMOTE FATAL_ERROR WARN WARN)
run_test(DEMOTE FATAL_ERROR SEND_ERROR SEND_ERROR)
run_test(DEMOTE FATAL_ERROR FATAL_ERROR FATAL_ERROR)