Best way to snapshot test STDOUT?

[spenserblack]

I'm a beginner to Ruby, so I don't know the best way to do this. What would be the best way to make a snapshot test for a method that would typically output to STDOUT (in my case, MyGem::CLI.start)?

Would it also be reasonable for this to be a feature request? RSpec has .output(/pattern/).to_stdout (and .to_stderr), so would it be reasonable (or possible) to support something like this?

expect { foo }.to match_stdout_snapshot('foo_stdout_snapshot_1')

Edit: I'm reassigning $stdout to a StringIO instance, but I'm wondering if this should be built-in.