FlexMock 1.0.0 Released

= FlexMock 1.0.0 Released

FlexMock is a flexible mocking library for use in unit testing and
behavior specification in Ruby. Release 1.0.0 is a minor release with
a few bug fixes.

== Changes in 1.0.0

=== Features

  • Mocks may now have a base class that limits what methods may be
    mocked. This allows early detection of outdated mock setups when the
    methods in the class are refactored.

  • Spy assertions are now allowed. The verification of the calling of
    mocked methods may now be done in the “then” portion of the test,
    after the code under test has been run. This allows for much more
    natural Given/When/Then style testing.

  • A custom assert method (assert_spy_called) has been added to make
    spy assertions easy when using Test::Unit or MiniTest.

  • An RSpec matcher (have_received) has been added to make spy
    assertions easy when using RSpec.

=== Bug Fixes

  • Now correctly handling the mocking of meta-programmed methods.

  • Using the documented +singleton_methods+ method.

  • Accidently trying to partial mock a regular mock is now a no-op.

== What is FlexMock?

FlexMock is a flexible framework for creating mock object for testing.
When running unit tests, it is often desirable to use isolate the
objects being tested from the “real world” by having them interact
with simplified test objects. Sometimes these test objects simply
return values when called, other times they verify that certain
methods were called with particular arguments in a particular order.

FlexMock makes creating these test objects easy.

=== Features

  • Easy integration with both Test::Unit and RSpec. Mocks created with
    flexmock method are automatically verified at the end of the test or

  • A fluent interface that allows mock behavior to be specified very

  • A “record mode” where an existing implementation can record its
    interaction with a mock for later validation against a new

  • Easy mocking of individual methods in existing, non-mock objects.

  • Easy mocking of chains of method calls.

  • The ability to cause classes to instantiate test instances (instead of
    instances) for the duration of a test.

=== Example

Suppose you had a Dog object that wagged a tail when it was happy.
Something like this:

class Dog
def initialize(a_tail)
@tail = a_tail
def happy

To test the +Dog+ class without a real +Tail+ object (perhaps because
real +Tail+ objects activate servos in some robotic equipment), you
can do something like this:

RSpec.configure do |config|
config.mock_with :flexmock

describe Dog do
it “wags its tail when happy” do
tail = flexmock(“tail”)
dog = Dog.new(tail)

FlexMock will automatically verify that the mocked tail object received
message +wag+ exactly one time. If it doesn’t, the test will not pass.

Here’s the same thing using the new spy support:

describe Dog do
it “wags its tail when happy” do
tail = flexmock(“tail”)
dog = Dog.new(tail)
tail.should have_received(:wag)

This style works particularly well with the rspec-given library.

require ‘rspec/given’

describe Dog do
context “when the dog is happy” do
Given(:tail) { flexmock(:on, Tail) }
Given(:dog) { Dog.new(tail) }

  When { dog.happy }

  Then { tail.should have_received(:wag) }


See the FlexMock documentation at http://flexmock.rubyforge.org for
details on
specifying arguments and return values on mocked methods, as well as a
technique for mocking tail objects when the Dog class creates the tail

== Availability

You can make sure you have the latest version with a quick RubyGems

gem install flexmock (you may need root/admin privileges)

You will find documentation at: http://flexmock.rubyforge.org.

– Jim W.