dominoes: sync

[senekor]

[no important files changed]

part of #1824

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

For more information, refer to the documentation. If you are unsure whether to add the message or not, please ping @exercism/maintainers-admin in a comment. Thank you!

[senekor]

There is complicated validation logic here, which didn't make sense to copy-paste into every test case. But I didn't want to completely delete it either, because it produces nice error messages that can point users in the right direction about what went wrong.

As a compromise, I added a technically redundant assert!(output.is_some()) above the calls to assert_correct. Once the test code is included in the test runner, users will at least know whether Some or None was expected. How exactly the error message was produced - for that they'd need to open the test file.