Improve testing coverage

[rhysyngsun]

Our testing coverage is sitting at ~82% as of this writing, we should try to improve that, so we should have some goals:

• 85% coverage
• 90% coverage - Improve testing coverage to 90% #2374
• 95% coverage
• 100% coverage

Historically, most of our other projects hover around 95%, but 100% coverage is achievable by annotate lines that are difficult or impossible to cover with # pragma: no cover. This annotation should be used very sparingly.

• Improve testing coverage - cov-fail-under setting #2097 - Additionally, we should add the flag --cov-fail-under=NN for our baseline coverage percentage, increasing it as we work our way to 100% coverage

[briangrossman]

For reference: While not perfect, there's data here: https://codecov.io/gh/mitodl/mitxpro

[HamzaIbnFarooq]

Here is a list of all the files which have code coverage less than 85:

affiliate/apps.py                                           3      3      0      0     0.00%   2-8
authentication/apps.py                                      3      3      0      0     0.00%   2-8
compliance/apps.py                                          3      3      0      0     0.00%   2-8
repl.py                                                    14     14      6      0     0.00%   2-28
users/apps.py                                               3      3      0      0     0.00%   2-8
voucher/apps.py                                             3      3      0      0     0.00%   4-10
sheets/coupon_assign_api.py                               273    215    118      0    14.83%   67-72, 89-109, 119-120, 130-145, 163-190, 208, 226-227, 249, 272-273, 285, 295, 306-309, 333-352, 362-365, 393-406, 420-449, 466-497, 514, 544-547, 558, 568, 580-588, 608-609, 627-661, 671-683, 699-738, 753-754, 779-802, 819-829, 849-894, 911-948, 965-1027
sheets/refund_request_api.py                               91     65     20      0    23.42%   56-71, 85-113, 120, 139-149, 161-173, 187-189, 219-288
sheets/deferral_request_api.py                             69     49     16      0    23.53%   45-56, 70-94, 101, 124-211
sheets/mail_api.py                                         34     22     14      0    25.00%   39-85
sheets/tasks.py                                            80     52     20      0    28.00%   51-53, 63-65, 78-88, 107-122, 138-151, 160-164, 185-216, 228-237, 250-263
sheets/api.py                                             169    112     60      3    29.69%   62-72, 119->120, 120-122, 131->132, 132-134, 145-149, 162-163, 176-186, 202, 224, 246-249, 263, 283-284, 303-304, 324-351, 380-386, 418-426, 439-465, 486-550, 566->568, 568-572
cms/forms.py                                                6      3      2      0    37.50%   14-16
sheets/sheet_handler_api.py                               105     43     34      7    53.96%   47, 69, 95->97, 98->100, 101->102, 102-106, 108->109, 109, 124, 139, 156, 170, 186, 197->200, 200, 210-211, 219->206, 221->222, 222, 248-255, 259, 264, 275-276, 296-311, 314-334, 337
cms/embeds.py                                              25     12      4      0    58.62%   34-49
sheets/views.py                                            92     26     22      8    64.91%   41-45, 58->59, 59, 75->76, 76, 78->79, 79, 107->108, 108, 110->111, 111-115, 120-124, 126->127, 127-131, 141-148, 149->150, 150-157, 159->161, 161-165
compliance/admin.py                                        24      6      2      0    69.23%   27-32, 38, 42
sheets/exceptions.py                                       10      3      0      0    70.00%   28-30
cms/api.py                                                 86     15     44     14    71.54%   103->107, 107->108, 108, 111->115, 118->exit, 130->131, 131-132, 133->exit, 151->155, 155->156, 156-158, 160->164, 164->165, 165-167, 169->173, 173->174, 174-176, 178->189, 189->193, 193-195
sheets/utils.py                                           179     37     18      1    74.62%   56->57, 57, 95-99, 318-319, 346-360, 374-382, 395-396, 409, 424, 437, 495, 509-510, 523, 538, 556, 625-630
authentication/views.py                                    97     20     14      1    77.48%   63->66, 66, 147, 157-174, 178-180, 194-197, 221-224
users/management/commands/retire_users.py                  43      8      8      3    78.43%   49-51, 57, 73->74, 74-79, 85->86, 86-93, 112->117
sheets/admin.py                                            39      5      4      0    79.07%   55-64
users/utils.py                                             45      6     14      4    79.66%   109->116, 116->exit, 119->120, 120, 121->122, 122-131
cms/blocks.py                                              42      6      8      2    80.00%   70-74, 102->103, 103, 110->111, 111
cms/templatetags/image_version_url.py                      15      2      6      2    80.95%   27->28, 28, 30->31, 31
authentication/exceptions.py                               36      6      0      0    83.33%   13-14, 37, 44, 58, 65
cms/urls.py                                                10      1      2      1    83.33%   25->30, 30
authentication/strategy.py                                 15      1      4      2    84.21%   18->21, 25->26, 26