ANN: FlexMock 0.6.0 Released

= FlexMock 0.6.0 Released

FlexMock is a flexible mocking library for use in unit testing and
behavior specification in Ruby. Version 0.6.0 introduces a number of
API enhancements to make testing with mocks even easier than before.

== New in 0.6.0

* Better integration with Test::Unit (no need to explicitly include

* Integration with RSpec (version 0.9.0 or later of RSpec is required).

* The +flexmock+ method will now create both regular mocks and partial

     flexmock() # => a full mock
     flexmock(person) # => a partial mock based on person

  (+flexstub+ is still included for backwards compatibility).

* Quick and simple mocks my now be created using an expectation hash.

    flexmock(:foo => 10, :bar => "Hello")

  will create a mock with two methods, :foo and :bar,defined. :foo will
  return 10 when invoked, and :bar will return "Hello".

* The +should_receive+ method will now allow multiple methods (with the
  constraints) be defined in a single call. For example, the following
  declares that both :read and :write need to be called at least one
time each
  on the mock object.

    flexmock.should_receive(:read, :write).at_least.once

* +should_recieve+ now will allow expectation hashes as arguments. This
  similar to the list of methods, but allows each defined method to have
  own return value.

    flexmock.should_receive(:name => "John", :age => 32)

* In addition to using a block for defining constrains, constraints may
now be
  applied directly to the return value of +new_instances+. Combined with
  expectation hashes supported by +should_receive+, simple mocking
  have become much more succinct. For example:

      flexmock(Person).new_instances.should_receive(:name => "John",
:age => 32)

* Improved implementation, allowing for more flexible use and greater
  consistency between full mock and partial mocks.

* Version 0.6.0 also includes a fix for an incompatibility with some
  versions of RCov. The FlexMock Rakefile now includes a RCov task (and
  have 100% code coverage).

== What is FlexMock?

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

* 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:

require 'test/unit'
require 'flexmock/test_unit'

  class TestDog < Test::Unit::TestCase
    def test_dog_wags_tail_when_happy
      tail = flexmock("tail")
      dog =

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

See the FlexMock documentation at 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)

Otherwise, you can get it from the more traditional places:


You will find documentation at:

-- Jim Weirich


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