OSRA-207 Add 'Payment Plan' to Sponsor

OSRA-207
I finally hit upon the reason this doesn't sit right with me: I write tests to ensure that an app works the way it's intended to work, not that it doesn't fail in any one of a thousand specific ways it could fail. In this particular case, then, if selecting the blank value is somehow a special case (which I'm not convinced it needs to be), then I'd write a test specifically for selecting it. If the test fails because Capybara finds an ambiguous match, I'd go back and fix the code. 

The only times I've written tests to guard against a specific failure was while fixing bugs. The tests were written to reproduce the bug first and then to ensure that the fix worked.