gistfile1.rb

require 'test_helper'

class PayPalExpress::TransactionSearchTest < ActiveSupport::TestCase
  test "#search returns a collection of transactions" do
    account   = MiniTest::Mock.new
    period    = MiniTest::Mock.new
    requester = MiniTest::Mock.new
    params    = {}
    params['ACK']  = 'Success'
    params.default = []
    requester.expect :perform, params

    transaction_search = PayPalExpress::TransactionSearch.new :period => period, :account => account, :requester => requester
    transactions       = transaction_search.search

    assert_empty transactions
    requester.verify
  end

  test "#search sends an email when PayPal returns a failure" do
    account   = MiniTest::Mock.new
    period    = MiniTest::Mock.new
    requester = MiniTest::Mock.new
    notifier  = MiniTest::Mock.new
    notifier.expect :deliver
    params    = {}
    params['ACK']  = 'Error'
    params.default = []

    transaction_search = PayPalExpress::TransactionSearch.new :period => period, :account => account, :requester => requester
    transactions       = transaction_search.search

    assert notifier.verify
  end
end

Not sure how I came across this, but dig the badge.