Handle case where no test groups are runnable by students

[mimischly7]

Motivation and Context

In the autotest-settings page (in the instructor view), the instructor has the ability to make all test groups NOT-runnable by students. Currently, when a student presses the "Run Tests" button, a request is still sent to the auto-testing server and 0/0 is shown on the website. We want to change this so that, if no test-groups are student-runnable, we avoid the unnecessary request to the autotest server and present an appropriate message on the screen.

Your Changes

Description:
An Assignment object has a test_groups association (corresponding to a test_groups table in the postgres database) holding information about the autotest-settings set by the instructor for that assignment, including who can run the tests, which is an array equal to one of the four following: ["instructor", "student"], ["instructor"], ["student"], [].
In the execute_test_run action of the automated_tests_controller, we examine the test_groups attribute of the current assignment and if there is no test-group runnable by a student, we flash an appropriate message and return early.

Type of change (select all that apply):

• Bug fix (non-breaking change which fixes an issue)

Testing

I had to modify the current tests because this pull request does change the behavior of automated testing. In particular, if none of the test-groups are runnable by students, now the test-execution job does not get enqueued (which was the whole point, since if it gets enqueued to AutotestRunJob then an unnecessary request will be made to the autotest server). But this made some of the existing tests for execute_test_run (in automated_test_controller.rb) fail. This is because the factory-produced assignment object used in these tests had the test_groups attribute/association uninitialized (due to how an :assignment is spawned by a factory). To test the new behavior, instead of generating a simple :assignment, the tests now use an :assignment_with_criteria_and_test_results, and in the tests with context "when the student is allowed to run tests", I had to manually update the test_groups attribute of the assignment to specify that the test_group is runnable by students. Overall, we are now testing the case where none of the test groups are runnable by students, so no job should be enqueued, and the case where at least one test-group is student-runnable, in which case the job should be enqueued as usual.

Questions and Comments (if applicable)

Checklist

• I have performed a self-review of my own code.
• I have verified that the pre-commit.ci checks have passed.
• I have verified that the CI tests have passed.
• I have reviewed the test coverage changes reported on Coveralls.
• I have added tests for my changes.
• I have updated the Changelog.md file.

[david-yz-liu]

@mimischly7 good work, in addition to the comments I left, make the equivalent change for instructor-run tests.

[coveralls]

Pull Request Test Coverage Report for Build 8573068288

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 29 of 29 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 91.917%

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Totals
Change from base Build 8498218632:	0.3%
Covered Lines:	41077
Relevant Lines:	43986

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💛 - Coveralls