Testing a random transaction_id in RSpec

Question

I'm building an API POST call that includes data to be sent in the call. One piece of that data is a transaction_id, which I'm creating using the following code:

transaction_id = Digest::SHA1.hexdigest([Time.now, rand].join)[0..10].to_i(16).to_s(10)

I'm also using RSpec 2.12.2, which doesn't have allow defined yet, so I can't do or even test something like

allow(Digest::SHA1).to receive(:hexdigest).and_return("transaction_id")

How can I mock a transaction_id in RSpec? I can freeze time, but having the rand in [Time.now, rand] returns different results even if time is frozen.

Answer 1

I found that this works:

Digest::SHA1.any_instance.stubs(:hexdigest).returns("transaction_id")

based on examples here: https://github.com/freerange/mocha