require "../../spec_helper" class Phonebook def find(name) # Some expensive lookup call. "+18005554321" end end class Resolver def initialize(@phonebook : Phonebook) end def find(name) @phonebook.find(name) end end Spectator.describe Resolver do mock Phonebook do stub find(name) end describe "#find" do it "can find number" do pb = Phonebook.new allow(pb).to receive(find).and_return("+18005551234") resolver = Resolver.new(pb) expect(resolver.find("Bob")).to eq("+18005551234") end end end