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https://github.com/freerange/mocha

Mocha is a mocking and stubbing library for Ruby
https://github.com/freerange/mocha

minitest mock ruby stub test-unit testing

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Mocha is a mocking and stubbing library for Ruby

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## Mocha [![CircleCI status of freerange/mocha](https://circleci.com/gh/freerange/mocha.svg?style=shield)](https://app.circleci.com/pipelines/github/freerange/mocha) [![Gem Version](https://badge.fury.io/rb/mocha.svg)](http://badge.fury.io/rb/mocha)



### Description



* A Ruby library for [mocking](http://xunitpatterns.com/Mock%20Object.html) and [stubbing](http://xunitpatterns.com/Test%20Stub.html) - but deliberately not (yet) [faking](http://xunitpatterns.com/Fake%20Object.html) or [spying](http://xunitpatterns.com/Test%20Spy.html).

* A unified, simple and readable syntax for both full & partial mocking.

* Built-in support for Minitest and Test::Unit.

* Supported by many other test frameworks.



### Intended Usage

Mocha is intended to be used in unit tests for the [Mock Object](http://xunitpatterns.com/Mock%20Object.html) or [Test Stub](http://xunitpatterns.com/Test%20Stub.html) types of [Test Double](http://xunitpatterns.com/Test%20Double.html), not the [Fake Object](http://xunitpatterns.com/Fake%20Object.html) or [Test Spy](http://xunitpatterns.com/Test%20Spy.html) types. Although it would be possible to extend Mocha to allow the implementation of fakes and spies, we have chosen to keep it focused on mocks and stubs.



### Installation



#### Gem



Install the latest version of the gem with the following command...



    $ gem install mocha



Note: If you are intending to use Mocha with Test::Unit or Minitest, you should only setup Mocha *after* loading the relevant test library...



##### Test::Unit



```ruby

require 'rubygems'

gem 'mocha'

require 'test/unit'

require 'mocha/test_unit'

```



##### Minitest



```ruby

require 'rubygems'

gem 'mocha'

require 'minitest/autorun'

require 'mocha/minitest'

```



#### Bundler



If you're using Bundler, include Mocha in the `Gemfile` and then setup Mocha later once you know the test library has been loaded...



##### Test::Unit



```ruby

# Gemfile

gem 'mocha'



# Elsewhere after Bundler has loaded gems e.g. after `require 'bundler/setup'`

require 'test/unit'

require 'mocha/test_unit'

```



##### Minitest



```ruby

# Gemfile

gem 'mocha'



# Elsewhere after Bundler has loaded gems e.g. after `require 'bundler/setup'`

require 'minitest/autorun'

require 'mocha/minitest'

```



##### RSpec



RSpec includes a mocha adapter. Just tell RSpec you want to mock with `:mocha`:



```ruby

# Gemfile in Rails app

gem 'mocha'



# Within `spec/spec_helper.rb`

RSpec.configure do |config|

  config.mock_with :mocha

end

```



Note: There is no need to use a require statement to setup Mocha; RSpec does this itself.



##### Cucumber



```ruby

# In e.g. features/support/mocha.rb

require 'mocha/api'



World(Mocha::API)



Around do |scenario, block|

  begin

    mocha_setup

    block.call

    mocha_verify

  ensure

    mocha_teardown

  end

end

```



#### Rails



If you're loading Mocha using Bundler within a Rails application, you should setup Mocha manually e.g. at the bottom of your `test_helper.rb`.



##### Minitest



Note that since Rails v4 (at least), `ActiveSupport::TestCase` has inherited from `Minitest::Test` or its earlier equivalents. Thus unless you are *explicitly* using Test::Unit, you are likely to be using Minitest.



```ruby

# Gemfile in Rails app

gem 'mocha'



# At bottom of test_helper.rb (or at least after `require 'rails/test_help'`)

require 'mocha/minitest'

```



##### Other Test Framework



Follow the instructions for the relevant test framework in the [Bundler](#bundler) section, but ensure that the relevant Mocha file (`mocha/minitest`, `mocha/test_unit`, or `mocha/api`) is required **after** the test framework has been loaded, e.g. at the bottom of `test_helper.rb` or `spec_helper.rb`, or at least after `rails/test_help` has been required.



#### Known Issues



* In Mocha v1.10.0 an undocumented feature of `API#mock`, `API#stub` & `API#stub_everything` was changed. Previously when these methods were passed a single symbol, they returned a mock object that responded to the method identified by the symbol. Now Passing a single symbol is equivalent to passing a single string, i.e. it now defines the 'name' of the mock object.

* In Mocha v1.2.0 there is a scenario where stubbing a class method originally defined in a module hangs the Ruby interpreter due to [a bug in Ruby v2.3.1](https://bugs.ruby-lang.org/issues/12832). See #272. This was fixed in Mocha v1.2.1.

* Since v1.1.0 Mocha has used prepended modules internally for stubbing methods. There is [an obscure Ruby bug](https://bugs.ruby-lang.org/issues/12876) in many (but not all) versions of Ruby between v2.0 & v2.3 which under certain circumstances may cause your Ruby interpreter to hang. See the Ruby bug report for more details. The bug has been fixed in Ruby v2.3.3 & v2.4.0.

* Stubbing an aliased class method, where the original method is defined in a module that's used to `extend` the class doesn't work in Ruby 1.8.x. See stub_method_defined_on_module_and_aliased_test.rb for an example of this behaviour.

* 0.13.x versions cause a harmless, but annoying, deprecation warning when used with Rails 3.2.0-3.2.12, 3.1.0-3.1.10 & 3.0.0-3.0.19.

* 0.11.x versions don't work with Rails 3.2.13 (`TypeError: superclass mismatch for class ExpectationError`). See #115.

* Versions 0.10.2, 0.10.3 & 0.11.0 of the Mocha gem were broken. Please do not use these versions.



### Usage



#### Quick Start



```ruby

require 'test/unit'

require 'mocha/test_unit'



class MiscExampleTest < Test::Unit::TestCase

  def test_mocking_a_class_method

    product = Product.new

    Product.expects(:find).with(1).returns(product)

    assert_equal product, Product.find(1)

  end



  def test_mocking_an_instance_method_on_a_real_object

    product = Product.new

    product.expects(:save).returns(true)

    assert product.save

  end



  def test_stubbing_instance_methods_on_real_objects

    prices = [stub(pence: 1000), stub(pence: 2000)]

    product = Product.new

    product.stubs(:prices).returns(prices)

    assert_equal [1000, 2000], product.prices.collect {|p| p.pence}

  end



  def test_stubbing_an_instance_method_on_all_instances_of_a_class

    Product.any_instance.stubs(:name).returns('stubbed_name')

    product = Product.new

    assert_equal 'stubbed_name', product.name

  end



  def test_traditional_mocking

    object = mock('object')

    object.expects(:expected_method).with(:p1, :p2).returns(:result)

    assert_equal :result, object.expected_method(:p1, :p2)

  end



  def test_shortcuts

    object = stub(method1: :result1, method2: :result2)

    assert_equal :result1, object.method1

    assert_equal :result2, object.method2

  end

end

```



#### Mock Objects



```ruby

class Enterprise

  def initialize(dilithium)

    @dilithium = dilithium

  end



  def go(warp_factor)

    warp_factor.times { @dilithium.nuke(:anti_matter) }

  end

end



require 'test/unit'

require 'mocha/test_unit'



class EnterpriseTest < Test::Unit::TestCase

  def test_should_boldly_go

    dilithium = mock()

    dilithium.expects(:nuke).with(:anti_matter).at_least_once  # auto-verified at end of test

    enterprise = Enterprise.new(dilithium)

    enterprise.go(2)

  end

end

```



#### Partial Mocking



```ruby

class Order

  attr_accessor :shipped_on



  def total_cost

    line_items.inject(0) { |total, line_item| total + line_item.price } + shipping_cost

  end



  def total_weight

    line_items.inject(0) { |total, line_item| total + line_item.weight }

  end



  def shipping_cost

    total_weight * 5 + 10

  end



  class << self

    def find_all

      # Database.connection.execute('select * from orders...

    end



    def number_shipped_since(date)

      find_all.select { |order| order.shipped_on > date }.length

    end



    def unshipped_value

      find_all.inject(0) { |total, order| order.shipped_on ? total : total + order.total_cost }

    end

  end

end



require 'test/unit'

require 'mocha/test_unit'



class OrderTest < Test::Unit::TestCase

  # illustrates stubbing instance method

  def test_should_calculate_shipping_cost_based_on_total_weight

    order = Order.new

    order.stubs(:total_weight).returns(10)

    assert_equal 60, order.shipping_cost

  end



  # illustrates stubbing class method

  def test_should_count_number_of_orders_shipped_after_specified_date

    now = Time.now; week_in_secs = 7 * 24 * 60 * 60

    order_1 = Order.new; order_1.shipped_on = now - 1 * week_in_secs

    order_2 = Order.new; order_2.shipped_on = now - 3 * week_in_secs

    Order.stubs(:find_all).returns([order_1, order_2])

    assert_equal 1, Order.number_shipped_since(now - 2 * week_in_secs)

  end



  # illustrates stubbing instance method for all instances of a class

  def test_should_calculate_value_of_unshipped_orders

    Order.stubs(:find_all).returns([Order.new, Order.new, Order.new])

    Order.any_instance.stubs(:shipped_on).returns(nil)

    Order.any_instance.stubs(:total_cost).returns(10)

    assert_equal 30, Order.unshipped_value

  end

end

```



### Thread safety



Mocha currently *does not* attempt to be thread-safe.



#### Can I test multi-threaded code with Mocha?



The short answer is no. In multi-threaded code Mocha exceptions may be raised in a thread other than the one which is running the test and thus a Mocha exception may not be correctly intercepted by Mocha exception handling code.



#### Can I run my tests across multiple threads?



Maybe, but probably not. Partial mocking changes the state of objects in the `ObjectSpace` which is shared across all threads in the Ruby process and this access to what is effectively global state is not synchronized. So, for example, if two tests are running concurrently and one uses `#any_instance` to modify a class, both tests will see those changes immediately.



### Expectation matching / invocation order



Stubs and expectations are basically the same thing. A stub is just an expectation of zero or more invocations. The `Expectation#stubs` method is syntactic sugar to make the intent of the test more explicit.



When a method is invoked on a mock object, the mock object searches through its expectations from newest to oldest to find one that matches the invocation. After the invocation, the matching expectation might stop matching further invocations.



See the [documentation](https://mocha.jamesmead.org/Mocha/Mock.html) for `Mocha::Mock` for further details.



### Configuration



If you want, Mocha can generate a warning or raise an exception when:



* stubbing a method unnecessarily

* stubbing method on a non-mock object

* stubbing a non-existent method

* stubbing a non-public method



See the [documentation](https://mocha.jamesmead.org/Mocha/Configuration.html) for `Mocha::Configuration` for further details.



##### MOCHA_OPTIONS

`MOCHA_OPTIONS` is an environment variable whose value can be set to a comma-separated list, so that we can specify multiple options e.g. `MOCHA_OPTIONS=debug,use_test_unit_gem`.

Only the following values are currently recognized and have an effect:

* `debug`: Enables a debug mode which will output backtraces for each deprecation warning. This is useful for finding where in the test suite the deprecated calls are.



### Semantic versioning



* Every effort is made to comply with [semantic versioning](https://semver.org/).

* However, this only applies to the behaviour documented in the public API.

* The documented public API does *not* include the content or format of messsages displayed to the user, e.g. assertion failure messages.



### Useful Links



* [Official Documentation](https://mocha.jamesmead.org)

* [Source Code](http://github.com/freerange/mocha)

* [Mailing List](http://groups.google.com/group/mocha-developer)

* [James Mead's Blog](http://jamesmead.org/blog/)

* [An Introduction To Mock Objects In Ruby](http://jamesmead.org/talks/2007-07-09-introduction-to-mock-objects-in-ruby-at-lrug/)

* [Mocks Aren't Stubs](http://martinfowler.com/articles/mocksArentStubs.html)

* [Growing Object-Oriented Software Guided By Tests](http://www.growing-object-oriented-software.com/)

* [Mock Roles Not Objects](http://www.jmock.org/oopsla2004.pdf)

* [jMock](http://www.jmock.org/)



### Contributors



See this [list of contributors](https://github.com/freerange/mocha/graphs/contributors).



### Releasing a new version



* Update the RELEASE.md file with a summary of changes

* Bump the version in `lib/mocha/version.rb`

* Commit & push to GitHub

* Check CircleCI build is passing - https://app.circleci.com/pipelines/github/freerange/mocha



* Generate documentation:



```bash

$ MOCHA_GENERATE_DOCS=true bundle install



$ MOCHA_GENERATE_DOCS=true rake generate_docs

```

* Commit documentation & push to GitHub

* Sign in to rubygems.org and find API key - https://rubygems.org/profile/edit



```bash

$ curl -u  -H 'OTP:' https://rubygems.org/api/v1/api_key.yaml > ~/.gem/credentials; chmod 0600 ~/.gem/credentials

```



* Release gem to Rubygems:



```bash

$ rake release

[runs tests]

mocha 1.2.0 built to pkg/mocha-1.2.0.gem.

Tagged v1.2.0.

Pushed git commits and tags.

Pushed mocha 1.2.0 to rubygems.org.

```



### History



Mocha was initially harvested from projects at [Reevoo](http://www.reevoo.com/). It's syntax is heavily based on that of [jMock](http://www.jmock.org).



### License



© Copyright James Mead 2006



You may use, copy and redistribute this library under the same terms as [Ruby itself](https://www.ruby-lang.org/en/about/license.txt) or under the [MIT license](https://mit-license.org/).