Permalink
Fetching contributors…
Cannot retrieve contributors at this time
201 lines (199 sloc) 8.86 KB
require 'spec/mocks/framework'
require 'spec/mocks/extensions/object'
module Spec
# == Mocks and Stubs
#
# RSpec will create Mock Objects and Stubs for you at runtime, or attach stub/mock behaviour
# to any of your real objects (Partial Mock/Stub). Because the underlying implementation
# for mocks and stubs is the same, you can intermingle mock and stub
# behaviour in either dynamically generated mocks or your pre-existing classes.
# There is a semantic difference in how they are created, however,
# which can help clarify the role it is playing within a given spec.
#
# == Mock Objects
#
# Mocks are objects that allow you to set and verify expectations that they will
# receive specific messages during run time. They are very useful for specifying how the subject of
# the spec interacts with its collaborators. This approach is widely known as "interaction
# testing".
#
# Mocks are also very powerful as a design tool. As you are
# driving the implementation of a given class, Mocks provide an anonymous
# collaborator that can change in behaviour as quickly as you can write an expectation in your
# spec. This flexibility allows you to design the interface of a collaborator that often
# does not yet exist. As the shape of the class being specified becomes more clear, so do the
# requirements for its collaborators - often leading to the discovery of new types that are
# needed in your system.
#
# Read Endo-Testing[http://www.mockobjects.com/files/endotesting.pdf] for a much
# more in depth description of this process.
#
# == Stubs
#
# Stubs are objects that allow you to set "stub" responses to
# messages. As Martin Fowler points out on his site,
# mocks_arent_stubs[http://www.martinfowler.com/articles/mocksArentStubs.html].
# Paraphrasing Fowler's paraphrasing
# of Gerard Meszaros: Stubs provide canned responses to messages they might receive in a test, while
# mocks allow you to specify and, subsquently, verify that certain messages should be received during
# the execution of a test.
#
# == Partial Mocks/Stubs
#
# RSpec also supports partial mocking/stubbing, allowing you to add stub/mock behaviour
# to instances of your existing classes. This is generally
# something to be avoided, because changes to the class can have ripple effects on
# seemingly unrelated specs. When specs fail due to these ripple effects, the fact
# that some methods are being mocked can make it difficult to understand why a
# failure is occurring.
#
# That said, partials do allow you to expect and
# verify interactions with class methods such as +#find+ and +#create+
# on Ruby on Rails model classes.
#
# == Further Reading
#
# There are many different viewpoints about the meaning of mocks and stubs. If you are interested
# in learning more, here is some recommended reading:
#
# * Mock Objects: http://www.mockobjects.com/
# * Endo-Testing: http://www.mockobjects.com/files/endotesting.pdf
# * Mock Roles, Not Objects: http://www.mockobjects.com/files/mockrolesnotobjects.pdf
# * Test Double Patterns: http://xunitpatterns.com/Test%20Double%20Patterns.html
# * Mocks aren't stubs: http://www.martinfowler.com/articles/mocksArentStubs.html
#
# == Creating a Mock
#
# You can create a mock in any specification (or setup) using:
#
# mock(name, options={})
#
# The optional +options+ argument is a +Hash+. Currently the only supported
# option is +:null_object+. Setting this to true instructs the mock to ignore
# any messages it hasn’t been told to expect – and quietly return itself. For example:
#
# mock("person", :null_object => true)
#
# == Creating a Stub
#
# You can create a stub in any specification (or setup) using:
#
# stub(name, stub_methods_and_values_hash)
#
# For example, if you wanted to create an object that always returns
# "More?!?!?!" to "please_sir_may_i_have_some_more" you would do this:
#
# stub("Mr Sykes", :please_sir_may_i_have_some_more => "More?!?!?!")
#
# == Creating a Partial Mock
#
# You don't really "create" a partial mock, you simply add method stubs and/or
# mock expectations to existing classes and objects:
#
# Factory.should_receive(:find).with(id).and_return(value)
# obj.stub!(:to_i).and_return(3)
# etc ...
#
# == Expecting Messages
#
# my_mock.should_receive(:sym)
# my_mock.should_not_receive(:sym)
#
# == Expecting Arguments
#
# my_mock.should_receive(:sym).with(*args)
# my_mock.should_not_receive(:sym).with(*args)
#
# == Argument Matchers
#
# Arguments that are passed to #with are compared with actual arguments received
# using == by default. In cases in which you want to specify things about the arguments
# rather than the arguments themselves, you can use any of RSpec's Expression Matchers.
# They don't all make syntactic sense (they were primarily designed for use with
# Spec::Expectations), but you are free to create your own custom Spec::Matchers.
#
# Spec::Mocks does provide one additional Matcher method named #ducktype.
#
# In addition, Spec::Mocks adds some keyword Symbols that you can use to
# specify certain kinds of arguments:
#
# my_mock.should_receive(:sym).with(no_args())
# my_mock.should_receive(:sym).with(any_args())
# my_mock.should_receive(:sym).with(1, kind_of(Numeric), "b") #2nd argument can any kind of Numeric
# my_mock.should_receive(:sym).with(1, boolean(), "b") #2nd argument can true or false
# my_mock.should_receive(:sym).with(1, /abc/, "b") #2nd argument can be any String matching the submitted Regexp
# my_mock.should_receive(:sym).with(1, anything(), "b") #2nd argument can be anything at all
# my_mock.should_receive(:sym).with(1, ducktype(:abs, :div), "b")
# #2nd argument can be object that responds to #abs and #div
#
# == Receive Counts
#
# my_mock.should_receive(:sym).once
# my_mock.should_receive(:sym).twice
# my_mock.should_receive(:sym).exactly(n).times
# my_mock.should_receive(:sym).at_least(:once)
# my_mock.should_receive(:sym).at_least(:twice)
# my_mock.should_receive(:sym).at_least(n).times
# my_mock.should_receive(:sym).at_most(:once)
# my_mock.should_receive(:sym).at_most(:twice)
# my_mock.should_receive(:sym).at_most(n).times
# my_mock.should_receive(:sym).any_number_of_times
#
# == Ordering
#
# my_mock.should_receive(:sym).ordered
# my_mock.should_receive(:other_sym).ordered
# #This will fail if the messages are received out of order
#
# == Setting Reponses
#
# Whether you are setting a mock expectation or a simple stub, you can tell the
# object precisely how to respond:
#
# my_mock.should_receive(:sym).and_return(value)
# my_mock.should_receive(:sym).exactly(3).times.and_return(value1, value2, value3)
# # returns value1 the first time, value2 the second, etc
# my_mock.should_receive(:sym).and_return { ... } #returns value returned by the block
# my_mock.should_receive(:sym).and_raise(error)
# #error can be an instantiated object or a class
# #if it is a class, it must be instantiable with no args
# my_mock.should_receive(:sym).and_throw(:sym)
# my_mock.should_receive(:sym).and_yield(values,to,yield)
# my_mock.should_receive(:sym).and_yield(values,to,yield).and_yield(some,other,values,this,time)
# # for methods that yield to a block multiple times
#
# Any of these responses can be applied to a stub as well, but stubs do
# not support any qualifiers about the message received (i.e. you can't specify arguments
# or receive counts):
#
# my_mock.stub!(:sym).and_return(value)
# my_mock.stub!(:sym).and_return(value1, value2, value3)
# my_mock.stub!(:sym).and_raise(error)
# my_mock.stub!(:sym).and_throw(:sym)
# my_mock.stub!(:sym).and_yield(values,to,yield)
# my_mock.stub!(:sym).and_yield(values,to,yield).and_yield(some,other,values,this,time)
#
# == Arbitrary Handling
#
# Once in a while you'll find that the available expectations don't solve the
# particular problem you are trying to solve. Imagine that you expect the message
# to come with an Array argument that has a specific length, but you don't care
# what is in it. You could do this:
#
# my_mock.should_receive(:sym) do |arg|
# arg.should be_an_istance_of(Array)
# arg.length.should == 7
# end
#
# Note that this would fail if the number of arguments received was different from
# the number of block arguments (in this case 1).
#
# == Combining Expectation Details
#
# Combining the message name with specific arguments, receive counts and responses
# you can get quite a bit of detail in your expectations:
#
# my_mock.should_receive(:<<).with("illegal value").once.and_raise(ArgumentError)
module Mocks
end
end