Not A Mock

A cleaner and DRYer alternative to mocking and stubbing with RSpec.

notahat.com/not_a_mock

A Quick Introduction

Mocking (Not)

When you’re setting up for a spec, you can ask that method calls on an object be recorded:

  object.track_methods(:name, :length)

Once your code has run, you can make assertions about what methods were called, what arguments they took, their results, etc.

  object.should have_received(:length).without_args.and_returned(42)
  object.should have_received(:name).twice

See NotAMock::Matchers for an explanation of the available assertions, plus Object#track_methods and Object#untrack_methods.

Stubbing

Stubbing Methods

You can replace a method on an object with a stub version like this:

  object.stub_method(:method => return_value)

Any call to method after this will return return_value without invoking the method’s usual code.

Calls to stub methods are recorded as if you had called track_methods on them, so you can make assertions about them as shown above.

See Object#stub_methods, Object#unstub_methods.

Stubbing Objects

You can also replace an entire object with a stub version like this:

  my_object = MyClass.stub_instance(:method_a => return_value, :method_b => return_value, ...)

The returned my_object is a stub instance of MyClass with the given methods defined to provide the corresponding return values.

See Object.stub_instance.

Stubbing ActiveRecord Instances

When you call stub_instance on an ActiveRecord::Base subclass, Not A Mock automatically provides an id method and generates an id for the object.

Installation

(The following describes using NotAMock with Rails. It should also be possible to use it outside of Rails, but I haven’t tried it.)

First, install the rspec and rspec_on_rails plugins:

  ruby script/plugin install http://rspec.rubyforge.org/svn/tags/CURRENT/rspec
  ruby script/plugin install http://rspec.rubyforge.org/svn/tags/CURRENT/rspec_on_rails
  ruby script/generate rspec

(See rspec.info/documentation/rails/install.html for more details.)

Second, install the not_a_mock plugin:

  ruby script/plugin install git://github.com/notahat/not_a_mock.git

Finally, add the following to your project’s spec/spec_helper.rb:

  config.mock_with NotAMock::RspecMockFrameworkAdapter

Contributing

Send bugs, patches, and suggestions to Pete Yandell (pete@notahat.com)

Thanks to Pat Allan and Steve Hayes for contributing patches.