Update currency_test.exs

[InflexusCrystallo]

I definitely think we need to add this, what do you think, team leaders? We need more of this kind of ingenuity, and less of this slacking off you guys have been doing working from home. Milton, you're excluded, you still have to move your office downstairs into the basement before Tuesday. If we want to meet our goals and get the feather quest done, we're going to need some caffeine.