How do I stub things in MiniTest?

Question

Within my test I want to stub a canned response for any instance of a class.

It might look like something like:

Book.stubs(:title).any_instance().ret         


        

Answer 1

I thought I'd share an example that I built upon the answers here.

I needed to stub a method at the end of a long chain of methods. It all started with a new instance of a PayPal API wrapper. The call I needed to stub was essentially:

paypal_api = PayPal::API.new
response = paypal_api.make_payment
response.entries[0].details.payment.amount

I created a class that returned itself unless the method was amount:

paypal_api = Class.new.tap do |c|
  def c.method_missing(method, *_)
    method == :amount ? 1.25 : self
  end
end

Then I stubbed it in to PayPal::API:

PayPal::API.stub :new, paypal_api do
  get '/paypal_payment', amount: 1.25
  assert_equal 1.25, payments.last.amount
end

You could make this work for more than just one method by making a hash and returning hash.key?(method) ? hash[method] : self.