Clarify tests about parsing aliases

[amomchilov]

Split from #567.

These tests don't really have actually anything special to do with recursion. The behaviour being asserted is about how any kind of alias works.

[tenderlove]

These tests don't really have actually anything special to do with recursion.

This isn't 100% true. The test implicitly asserted that Psych.dump([].tap { |x| x << x }) would emit an alias. We know that an alias was emitted because we explicitly did not allow loading aliases and an exception was raised.

Can you make sure that we assert that Psych.dump([].tap { |x| x << x }) will use aliases?

[amomchilov]

Can you make sure that we assert that Psych.dump([].tap { |x| x << x }) will use aliases?

Good point. I added tests that ensures this, explicitly, not just for arrays, but also for hashes and object.

[tenderlove]

I don't think we should hard-code the expected YAML. We may want to change the emitted aliases in the future, and now this test couples the implementation with the exact alias name. IOW I want to test that aliases were used, but I don't care what the aliases were.

Not to mention, we may change indentation in the future etc, so I don't want the test to be coupled to the formatting either.

[amomchilov]

Done, what do you think? b9ab190