Class Mocha::Mock
In: lib/mocha/mock.rb
Parent: Object

Traditional mock object.

All methods return an {Expectation} which can be further modified by methods on {Expectation}.

Stubs and expectations are basically the same thing. A stub is just an expectation of zero or more invocations. The {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. For example, an +expects(:foo).once+ expectation only matches once and will be ignored on future invocations while an +expects(:foo).at_least_once+ expectation will always be matched against invocations.

This scheme allows you to:

  • Set up default stubs in your the setup method of your test class and override some of those stubs in individual tests.
  • Set up different once expectations for the same method with different action per invocation. However, it‘s better to use the {Expectation#returns} method with multiple arguments to do this, as described below.

However, there are some possible "gotchas" caused by this scheme:

  • if you create an expectation and then a stub for the same method, the stub will always override the expectation and the expectation will never be met.
  • if you create a stub and then an expectation for the same method, the expectation will match, and when it stops matching the stub will be used instead, possibly masking test failures.
  • if you create different expectations for the same method, they will be invoked in the opposite order than that in which they were specified, rather than the same order.

The best thing to do is not set up multiple expectations and stubs for the same method with exactly the same matchers. Instead, use the {Expectation#returns} method with multiple arguments to create multiple actions for a method. You can also chain multiple calls to {Expectation#returns} and {Expectation#raises} (along with syntactic sugar {Expectation#then} if desired).

@example

  object = mock()
  object.stubs(:expected_method).returns(1, 2).then.raises(Exception)
  object.expected_method # => 1
  object.expected_method # => 2
  object.expected_method # => raises exception of class Exception1

If you want to specify more complex ordering or order invocations across different mock objects, use the {Expectation#in_sequence} method to explicitly define a total or partial ordering of invocations.

Methods

Attributes

everything_stubbed  [R]  @private

Public Class methods

Public Instance methods

__expects__(method_name_or_hash, backtrace = nil)

Alias for expects

__stubs__(method_name_or_hash, backtrace = nil)

Alias for stubs

Adds an expectation that the specified method must be called exactly once with any parameters.

@param [Symbol,String] method_name name of expected method @param [Hash] expected_methods_vs_return_values expected method name symbols as keys and corresponding return values as values - these expectations are setup as if {expects} were called multiple times.

@overload def expects(method_name) @overload def expects(expected_methods_vs_return_values) @return [Expectation] last-built expectation which can be further modified by methods on {Expectation}.

@example Expected method invoked once so no error raised

  object = mock()
  object.expects(:expected_method)
  object.expected_method

@example Expected method not invoked so error raised

  object = mock()
  object.expects(:expected_method)
  # error raised when test completes, because expected_method not called exactly once

@example Expected method invoked twice so error raised

  object = mock()
  object.expects(:expected_method)
  object.expected_method
  object.expected_method # => error raised when expected method invoked second time

@example Setup multiple expectations using expected_methods_vs_return_values.

  object = mock()
  object.expects(:expected_method_one => :result_one, :expected_method_two => :result_two)

  # is exactly equivalent to

  object = mock()
  object.expects(:expected_method_one).returns(:result_one)
  object.expects(:expected_method_two).returns(:result_two)

@private

@private rubocop:disable Style/MethodMissingSuper

quacks_like(responder)

Alias for responds_like

quacks_like_instance_of(responder_class)

Constrains the {Mock} instance so that it can only expect or stub methods to which responder responds. The constraint is only applied at method invocation time.

A NoMethodError will be raised if the responder does not +respond_to?+ a method invocation (even if the method has been expected or stubbed).

The {Mock} instance will delegate its +respond_to?+ method to the responder.

Note that the methods on responder are never actually invoked.

@param [Object, respond_to?] responder an object used to determine whether {Mock} instance should +respond_to?+ to an invocation. @return [Mock] the same {Mock} instance, thereby allowing invocations of other {Mock} methods to be chained. @see responds_like_instance_of

@example Normal mocking

  sheep = mock('sheep')
  sheep.expects(:chew)
  sheep.expects(:foo)
  sheep.respond_to?(:chew) # => true
  sheep.respond_to?(:foo) # => true
  sheep.chew
  sheep.foo
  # no error raised

@example Using {responds_like} with an instance method

  class Sheep
    def chew(grass); end
  end

  sheep = mock('sheep')
  sheep.responds_like(Sheep.new)
  sheep.expects(:chew)
  sheep.expects(:foo)
  sheep.respond_to?(:chew) # => true
  sheep.respond_to?(:foo) # => false
  sheep.chew
  sheep.foo # => raises NoMethodError exception

@example Using {responds_like} with a class method

  class Sheep
    def self.number_of_legs; end
  end

  sheep_class = mock('sheep_class')
  sheep_class.responds_like(Sheep)
  sheep_class.stubs(:number_of_legs).returns(4)
  sheep_class.expects(:foo)
  sheep_class.respond_to?(:number_of_legs) # => true
  sheep_class.respond_to?(:foo) # => false
  sheep_class.number_of_legs # => 4
  sheep_class.foo # => raises NoMethodError exception

Constrains the {Mock} instance so that it can only expect or stub methods to which an instance of the responder_class responds. The constraint is only applied at method invocation time. Note that the responder instance is instantiated using +Class#allocate+.

A NoMethodError will be raised if the responder instance does not +respond_to?+ a method invocation (even if the method has been expected or stubbed).

The {Mock} instance will delegate its +respond_to?+ method to the responder instance.

Note that the methods on the responder instance are never actually invoked.

@param [Class] responder_class a class used to determine whether {Mock} instance should +respond_to?+ to an invocation. @return [Mock] the same {Mock} instance, thereby allowing invocations of other {Mock} methods to be chained. @see responds_like

@example Using {responds_like_instance_of}

  class Sheep
    def initialize
      raise "some awkward code we don't want to call"
    end
    def chew(grass); end
  end

  sheep = mock('sheep')
  sheep.responds_like_instance_of(Sheep)
  sheep.expects(:chew)
  sheep.expects(:foo)
  sheep.respond_to?(:chew) # => true
  sheep.respond_to?(:foo) # => false
  sheep.chew
  sheep.foo # => raises NoMethodError exception

Adds an expectation that the specified method may be called any number of times with any parameters.

@param [Symbol,String] method_name name of stubbed method @param [Hash] stubbed_methods_vs_return_values stubbed method name symbols as keys and corresponding return values as values - these stubbed methods are setup as if {stubs} were called multiple times.

@overload def stubs(method_name) @overload def stubs(stubbed_methods_vs_return_values) @return [Expectation] last-built expectation which can be further modified by methods on {Expectation}.

@example No error raised however many times stubbed method is invoked

  object = mock()
  object.stubs(:stubbed_method)
  object.stubbed_method
  object.stubbed_method
  # no error raised

@example Setup multiple expectations using stubbed_methods_vs_return_values.

  object = mock()
  object.stubs(:stubbed_method_one => :result_one, :stubbed_method_two => :result_two)

  # is exactly equivalent to

  object = mock()
  object.stubs(:stubbed_method_one).returns(:result_one)
  object.stubs(:stubbed_method_two).returns(:result_two)

Removes the specified stubbed method (added by calls to {expects} or {stubs}) and all expectations associated with it.

@param [Symbol] method_name name of method to unstub.

@example Invoking an unstubbed method causes error to be raised

  object = mock('mock') do
  object.stubs(:stubbed_method).returns(:result_one)
  object.stubbed_method # => :result_one
  object.unstub(:stubbed_method)
  object.stubbed_method # => unexpected invocation: #<Mock:mock>.stubbed_method()

[Validate]