Update docs/tutorial/writing-tests/test-case.rst

Co-authored-by: Pierre Equoy <[email protected]>

docs/tutorial/writing-tests/test-case.rst

@@ -1006,7 +1006,7 @@ following:
     # in
     (checkbox_venv) > python3 -m coverage html
 
-As you can see we are way below the coverage target but this is difficult to
+As you can see we are way below the coverage target (90%) but this is difficult to
 fix, we should add an end to end test of the main function, so that we
 cover it but, most importantly, we leave trace in the test file of an expected
 usage of the script. Add the following to ``tests/test_network_available.py``