from nbdev import *
from datetime import datetime

with open('70_multi_all_test_flag.txt','w') as f:
    f.write(str(datetime.now())+'\n')

The next section checks that flagged tests are run correctly. Any of the following should pass;

clear

rm 70_multi_all_test_flag.txt
nbdev_test_nbs --flags "slow" --fname 70_multi_all_test_flag.ipynb
cat 70_multi_all_test_flag.txt

nbdev_test_nbs --flags "cython" --fname 70_multi_all_test_flag.ipynb
cat 70_multi_all_test_flag.txt

nbdev_test_nbs --flags "cython slow" --fname 70_multi_all_test_flag.ipynb
cat 70_multi_all_test_flag.txt

but these should fail;

export EXEPECTED_TST_FLAGS="slow"
nbdev_test_nbs --flags "cython slow" --fname 30_test_flag.ipynb

export EXEPECTED_TST_FLAGS="cython slow"
nbdev_test_nbs --flags "slow" --fname 30_test_flag.ipynb

export EXEPECTED_TST_FLAGS="cython slow"
nbdev_test_nbs --fname 30_test_flag.ipynb