CROSS-STUB makes cross process stubbing possible !!

Introduction

Existing mocking/stubbing frameworks support only stubbing in the current process. This is OK most of the time. However, when running cucumber integration test suite in another process, these in-process stubbing frameworks simply doesn’t help. Eg. I want Time.now to always return a timing that should be a Sunday, how do I do that when running cucumber using selenium, culerity, steam, blah, blah driver? It doesn’t seem straight-forward me.

(Let’s not argue whether stubbing should be encouraged. It is an itch, the poor itch needs to be scratched.)

Getting Started

It’s hosted on gemcutter.org.

$ gem install cross-stub

Setting Up

#1. Rails:

$ ./script/generate cucumber
$ ./script/generate cross_stub

#2. Others (back to basics):

# In the test setup method:
CrossStub.setup :file => <CACHE_FILE>

# In the test teardown method:
CrossStub.clear

# Find an entry point in your target application, eg. in a server, the
# point where all request handling starts:
CrossStub.refresh :file => <CACHE_FILE>

For a full list of available cache stores, scroll down to take a look at the ‘Cache Stores’ section.

Using It

Cross-stubbing is simple:

#1. Simple returning of nil or non-nil value:

#1.1. Class method:

class Someone
  def self.say
    'hello'
  end
end

Someone.xstub(:say)
Someone.say # yields: nil

Someone.xstub(:say => 'HELLO')
Someone.say # yields: 'HELLO'

#1.2. Instance method:

Someone.xstub(:say, :instance => true)
Someone.new.say # yields: nil

Someone.xstub({:say => 'HELLO'}, :instance => true)
Someone.new.say # yields: 'HELLO'

#2. If a stubbed method requires argument, pass xstub a proc:

#2.1. Class method:

Someone.xstub do
  def say(something)
    'saying "%s"' % something
  end
end

Someone.say('HELLO') # yields: 'saying "HELLO"'

#2.2. Instance method:

Someone.xstub(:instance => true) do
  def say(something)
    'saying "%s"' % something
  end
end

Someone.new.say('HELLO') # yields: 'saying "HELLO"'

#3. Something more complicated:

something = 'hello'
Someone.xstub do
  def say
    'saying "%s"' % something
  end
end

Someone.say # failure !!

The above fails as a result of undefined variable/method ‘something’, to workaround we can have:

Someone.xstub(:something => 'HELLO') do
  def say
    'saying "%s"' % something
  end
end

Someone.say # yields: 'saying "HELLO"'

Cache Stores

Cache stores are needed to allow stubs to be made available for different processes. The following describes all cache stores available:

#1. File

# Setting up (current process)
CrossStub.setup :file => '<CACHE_FILE>'

# Refreshing (other process)
CrossStub.refresh :file => '<CACHE_FILE>'

#2. Memcache (requires memcache-client gem)

# Setting up (current process)
CrossStub.setup :memcache => 'localhost:11211/<CACHE_ID>'

# Refreshing (other process)
CrossStub.refresh :memcache => 'localhost:11211/<CACHE_ID>'

#3. Redis (requires redis gem)

# Setting up (current process)
CrossStub.setup :redis => 'localhost:6379/<CACHE_ID>'

# Refreshing (other process)
CrossStub.refresh :redis => 'localhost:6379/<CACHE_ID>'

Adding new store is super easy (w.r.t testing & actual implementation), let me know if u need more :]

Caveats

#1. CrossStub uses ruby’s Marshal class to dump & load the stubs, thus it has the same limitations as Marshal (pls note abt a 1.9.1 specific marshal bug at redmine.ruby-lang.org/issues/show/3729)

#2. Under the hood, CrossStub uses Sourcify (github.com/ngty/sourcify) for extracting the methods defined within the proc, u may wish to read Sourcify’s gotchas to avoid unnecessary headaches.

TODO(s)

#1. Is there any better serialization strategy instead of the current Marshal load/dump?

Contacts

Written since 2009 by:

#1. NgTzeYang, contact ngty77[at]gmailcom or github.com/ngty

#2. WongLiangZan, contact liangzan[at]gmailcom or github.com/liangzan

Released under the MIT license