Mocking with an alternative framework

In addition to rspec, mocha, flexmock, and RR, you can choose an alternate framework as the mocking framework. You (or the framework authors) just needs to provide an adapter that hooks RSpec’s events into those of the framework.

A mock framework adapter must expose three methods:

setup_mocks_for_rspec
- called before each example is run
verify_mocks_for_rspec
- called after each example is run
- this is where message expectation failures should result in an error with the appropriate failure message
teardown_mocks_for_rspec
- called after verify_mocks_for_rspec
- use this to clean up resources, restore objects to earlier state, etc
- guaranteed to run even if there are failures

Mock with alternate framework

Given a file named “expector.rb” with:

class Expector
  class << self
    def expectors
      @expectors ||= []
    end

    def clear_expectors
      expectors.clear
    end

    def verify_expectors
      expectors.each {|d| d.verify}
    end
  end

  def initialize
    self.class.expectors << self
  end

  def expectations
    @expectations ||= []
  end

  def expect(message)
    expectations << message.to_s
  end

  def verify
    unless expectations.empty?
      raise expectations.map {|e|
        "expected #{e}, but it was never received"
      }.join("\n")
    end
  end

private

  def method_missing(name, *args, &block)
    expectations.delete(name.to_s)
  end

public

  module RSpecAdapter
    def setup_mocks_for_rspec
      # no setup necessary
    end

    def verify_mocks_for_rspec
      Expector.verify_expectors
    end

    def teardown_mocks_for_rspec
      Expector.clear_expectors
    end
  end
end

Given a file named “example_spec.rb” with:

require File.expand_path("../expector", __FILE__)

RSpec.configure do |config|
  config.mock_with Expector::RSpecAdapter
end

RSpec.describe Expector do
  it "passes when message is received" do
    expector = Expector.new
    expector.expect(:foo)
    expector.foo
  end

  it "fails when message is received" do
    expector = Expector.new
    expector.expect(:foo)
  end
end

When I run rspec example_spec.rb --format doc

Then the exit status should be 1

And the output should contain “2 examples, 1 failure”

And the output should contain “fails when message is received (FAILED - 1)”.