Class: Mocha::Configuration

Inherits:
Object
  • Object
show all
Defined in:
lib/mocha/configuration.rb

Overview

This class allows you to determine what should happen under certain circumstances. In each scenario, Mocha can be configured to do nothing, display a warning message, or raise an exception. The relevant scenario is identified using one of the following symbols:

  • :stubbing_method_unnecessarily This is useful for identifying unused stubs. Unused stubs are often accidentally introduced when code is refactored. Allowed by default.

  • :stubbing_non_existent_method - This is useful if you want to ensure that methods you're mocking really exist. A common criticism of unit tests with mock objects is that such a test may (incorrectly) pass when an equivalent non-mocking test would (correctly) fail. While you should always have some integration tests, particularly for critical business functionality, this Mocha configuration setting should catch scenarios when mocked methods and real methods have become misaligned. Allowed by default.

  • :stubbing_non_public_method - Many people think that it's good practice only to mock public methods. This is one way to prevent your tests being too tightly coupled to the internal implementation of a class. Such tests tend to be very brittle and not much use when refactoring. Allowed by default.

  • :stubbing_method_on_non_mock_object - If you like the idea of mocking roles not objects and you don't like stubbing concrete classes, this is the setting for you. However, while this restriction makes a lot of sense in Java with its explicit interfaces, it may be moot in Ruby where roles are probably best represented as Modules. Allowed by default.

  • :stubbing_method_on_nil - This is usually done accidentally, but there might be rare cases where it is intended. Prevented by default.

Typically the configuration would be set globally in a test_helper.rb or spec_helper.rb file. However, it can also be temporarily overridden locally using the block syntax of the relevant method. In the latter case, the original configuration settings are restored when the block is exited.

Examples:

Preventing unnecessary stubbing of a method

Mocha::Configuration.prevent(:stubbing_method_unnecessarily)

example = mock('example')
example.stubs(:unused_stub)
# => Mocha::StubbingError: stubbing method unnecessarily:
# =>   #<Mock:example>.unused_stub(any_parameters)

Preventing stubbing of a method on a non-mock object

Mocha::Configuration.prevent(:stubbing_method_on_non_mock_object)

class Example
  def example_method; end
end

example = Example.new
example.stubs(:example_method)
# => Mocha::StubbingError: stubbing method on non-mock object:
# =>   #<Example:0x593620>.example_method

Preventing stubbing of a non-existent method


Mocha::Configuration.prevent(:stubbing_non_existent_method)

class Example
end

example = Example.new
example.stubs(:method_that_doesnt_exist)
# => Mocha::StubbingError: stubbing non-existent method:
# =>   #<Example:0x593760>.method_that_doesnt_exist

Preventing stubbing of a non-public method

Mocha::Configuration.prevent(:stubbing_non_public_method)

class Example
  def internal_method; end
  private :internal_method
end

example = Example.new
example.stubs(:internal_method)
# => Mocha::StubbingError: stubbing non-public method:
# =>   #<Example:0x593530>.internal_method

Temporarily allowing stubbing of a non-existent method

Mocha::Configuration.prevent(:stubbing_non_public_method)

class Example
end

Mocha::Configuration.allow(:stubbing_non_existent_method) do
  example = Example.new
  example.stubs(:method_that_doesnt_exist)
  # => no exception raised
end

Constant Summary collapse

DEFAULTS =
{
  :stubbing_method_unnecessarily => :allow,
  :stubbing_method_on_non_mock_object => :allow,
  :stubbing_non_existent_method => :allow,
  :stubbing_non_public_method => :allow,
  :stubbing_method_on_nil => :prevent
}.freeze

Class Method Summary collapse

Class Method Details

.allow(action) { ... } ⇒ Object

Allow the specified action.

Yields:

  • optional block during which the configuration change will be changed before being returned to its original value at the end of the block.


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# File 'lib/mocha/configuration.rb', line 82

def allow(action, &block)
  change_config action, :allow, &block
end

.prevent(action) { ... } ⇒ Object

Raise a StubbingError if if the specified action is attempted.

Yields:

  • optional block during which the configuration change will be changed before being returned to its original value at the end of the block.


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# File 'lib/mocha/configuration.rb', line 108

def prevent(action, &block)
  change_config action, :prevent, &block
end

.warn_when(action) { ... } ⇒ Object

Warn if the specified action is attempted.

Yields:

  • optional block during which the configuration change will be changed before being returned to its original value at the end of the block.


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# File 'lib/mocha/configuration.rb', line 95

def warn_when(action, &block)
  change_config action, :warn, &block
end