Floehopper: Tag ruby

Mocha Release 0.9.1

James Mead — Sat, 30 Aug 2008 16:48:00 +0000

Release Notes

Fixed bug #21465 – expects & stubs should support method names as strings (as well as symbols) or fail fast. Convert all expectation method names to a symbol in case they were supplied as a string.
By removing Mock#unexpected_method_called we reduce the number of methods vulnerable to the problem that surfaced in bug #21563.
Fix bug #21563 – stubbing ‘verified?’ method is unsafe. Instance method names on the Mock class should be more obscure.
Performance improvement. StubbaExampleTest goes twice as fast on my local machine.
Added primitive performance test to default rake task.
Fix format of case statements which don’t work in Ruby 1.9 and make others consistent.
There is no point in running (potentially expensive) checks if configuration is set to allow such checks to fail. This is a relatively quick fix in response to Chris McGrath’s performance problems.
Fix for bug #21161 – ‘uninitialized constant Deprecation in stubba.rb’.
It’s more readable to talk about ‘once’ and ‘twice’ rather than ‘1 time’ and ‘2 times’.
Fix bug #20883 – never should raise when called to prevent follow up errors. Fail fast when there are no matching invokable expectations and handle the stub_everything case sensibly. This might not be entirely backwards compatible, but I think the benefits outweigh the risks. The most likely change is that a test that was already failing will now fail faster, which doesn’t seem so awful.

Mocha 0.9 Released

James Mead — Tue, 24 Jun 2008 19:14:00 +0000

There’s been quite a bit of work going on in Mocha over recent months, but a release is long overdue. The API is now pretty stable and so this release jumps from version 0.5 to 0.9. Much of the work has been refactoring Mocha’s internals to support new features and make the code more maintainable.

Before attempting the refactoring, extensive acceptance tests were added. One of the benefits of this is that it should now be easier to write new acceptance tests if you want to suggest new features or illustrate a bug ;-)

Here’s a quick summary of the changes in the release. I’ll try to post some code examples here in the near future.

Ordering constraints

Based on the JMock constraints with the same names…

Added “sequences” for constraining the order of expected invocations. See Standalone#sequence and Expectation#in_sequence.
Added “states” for constraining the order of expected invocations. See Standalone#states, Expectation#then, Expectation#when and StateMachine.

Configurable warnings or errors

When a method on a non-public method is stubbed
When a method on a non-existent method is stubbed
When a method on a non-mock object is stubbed (partial mocking)
When a method is stubbed unnecessarily (i.e. the stubbed method is not called during the test)

See Configuration for more details.

Improved error messages

A more readable and complete list of unsatisfied expectations, satisfied expectations and state machines.
Display more sensible failure message for any_instance expectations.

Parameter matchers

New to this release: optionally (allows matching of optional parameters if available), yaml_equivalent (allows matching of YAML that represents the specified object), responds_with (tests the quack not the duck).
Nesting of matchers is now supported.

Syntax shortcut

An optional block can be passed into the Standalone#mock method. The block is evaluated in the context of the new mock instance and can be used as a shortcut to set up expectations.

Ruby & Rails compatibility

Tested with Ruby 1.8.4, 1.8.5, 1.8.6 & 1.9. All related bugs and warnings believed to be fixed.

Tested with Rails 1.2.3 & Rails 2.1.0.

Deprecation

There is no longer any need to have a “require ‘stubba’” statement in your code. A deprecation warning has been added to this effect, because the file will be removed in a future release.

Bug fixes

Mocha Mailing List Move

James Mead — Thu, 19 Jun 2008 20:32:38 +0000

The Mocha Mailing List has moved to Google Groups.

Group name: mocha-developer
Group home page: http://groups.google.com/group/mocha-developer
Group email address mocha-developer@googlegroups.com

Nasty Ruby Bug Affecting Test::Unit

James Mead — Sat, 05 Apr 2008 00:10:06 +0000

Introduction

Some time ago, while I was pair-programming with him, Chris alerted me to a Ruby bug he’d come across which was interfering with the diagnosis of a bug in our application. Since then I’ve tried to find out more about it, but couldn’t find much, so I’ve done a bit of investigation and thought I’d post it here in case it’s useful to anyone else. The bug has long since been fixed, but I’m sure there are still people our there with the affected versions of Ruby 1.8.6.

Ruby bug

As far as I understand it, the bug is in Ruby’s Kernel.at_exit hook. A call to Kernel.exit(false) should cause the process to exit with an exit status of 1 indicating the process did not complete successfully. The bug means that calling Kernel.exit(false) from within Kernel.at_exit incorrectly causes the process to exit with an exit status of 0.

The most relevant bug report is #9300 and the most relevant mailing list thread is made up of:- [ruby-core:10746], [ruby-core:10748], [ruby-core:10760].

The fix seems to be in changeset 12126…

r12126 | nobu | 2007-03-23 16:53:42 +0000 (Fri, 23 Mar 2007) | 9 lines

* eval.c (ruby_cleanup): exit by SystemExit and SignalException in END
  block.  [ruby-core:10609]

* test/ruby/test_beginendblock.rb (test_should_propagate_exit_code):
  test for exit in END block.  [ruby-core:10760]

* test/ruby/test_beginendblock.rb (test_should_propagate_signaled):
  test for signal in END block.

Implications for Test::Unit & Rake::TestTask

The bug has some important consequences. Test::Unit makes use of this mechanism to report test failures. Unfortunately, the bug means that a Test::Unit process will always return an exit status of 0 even when there have been test failures.

From test/unit.rb:

at_exit do
  unless $! || Test::Unit.run?
    exit Test::Unit::AutoRunner.run
  end
end

This in turn means that a Rake::TestTask process will also always return an exit status of 0 even when there have been test failures. This is significant, because many continuous integration systems rely on Rake::TestTask processes returning an exit status of 1 to indicate that there have been test failures. Thus you will get false positive passing builds – not good.

Affected versions of Ruby

I’ve built and installed a number of versions of Ruby and run tests on them to try to establish which ones are affected. Although they aren’t comprehensive, here are the results…

affected?	version
`N`	`ruby 1.8.4 (2005-12-24) [i686-darwin8.10.3]`
`N`	`ruby 1.8.5 (2006-08-25) [i686-darwin8.10.3]`
`N`	`ruby 1.8.5 (2007-03-16 patchlevel 37) [i686-darwin8.10.3]`
`N`	`ruby 1.8.5 (2008-03-03 patchlevel 115) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-02-17 patchlevel 0) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-03-16 patchlevel 2) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-03-19 patchlevel 4) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-05-22 patchlevel 5) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-05-22 patchlevel 6) [i686-darwin8.10.3]`
`Y`	`ruby 1.8.6 (2007-05-22 patchlevel 7) [i686-darwin8.10.3]`
`N`	`ruby 1.8.6 (2007-05-22 patchlevel 8) [i686-darwin8.10.3]`
`N`	`ruby 1.8.6 (2007-05-23 patchlevel 9) [i686-darwin8.10.3]`
`N`	`ruby 1.8.6 (2007-05-23 patchlevel 10) [i686-darwin8.10.3]`
`N`	`ruby 1.8.6 (2007-08-22 patchlevel 50) [i686-darwin8.10.3]`
`N`	`ruby 1.9.0 (2007-11-28 patchlevel 0) [i686-darwin8.10.3]`

Java Rehabilitation Clinic

James Mead — Mon, 17 Mar 2008 09:23:26 +0000

Not long after Ben persuaded me to join the fledgling Reevoo, we got our first big ReevooMark partners (Dixons & Currys) live. To celebrate this event and my having left Java behind at Thoughtworks, Ben bought me a Java Rehabilitation Clinic mug. The mug has recently developed a crack. I wonder if it’s trying to tell me it’s time to learn another language…

Java Rehabilitation Clinic mug

Mocking in Java using Mocha

James Mead — Sun, 17 Feb 2008 18:10:01 +0000

Ola Bini one of the JRuby guys has released the JtestR tool which allows you to write tests for Java code in Ruby! Ola has bundled a number of Ruby libraries – Mocha, RSpec, Dust, Test::Unit & ActiveSupport – together with JRuby to allow you to write Ruby test cases that test Java code.

He has a couple of examples in the Mock documentation of how to use Mocha...

The first one demonstrates using Mocha to mock an interface (Map).

  import java.util.Map
  import java.util.Iterator
  import java.util.Set
  import java.util.HashMap

  functional_tests do 
    test "that a new HashMap can be created based on another map" do 
      map = Map.new

      map.expects(:size).returns(0)

      iter = Iterator.new
      iter.expects(:hasNext).returns(false)

      set = Set.new
      set.expects(:iterator).returns(iter)

      map.expects(:entrySet).returns(set)

      assert_equals 0, HashMap.new(map).size
    end
  end

The second example demonstrates using Mocha to setup expectations on a real (non-mock) instance (HashMap)...

  import java.util.Iterator
  import java.util.Set
  import java.util.HashMap

  functional_tests do 
    test "that a new HashMap can be created based on another map" do 
      map = mock(HashMap)

      map.expects(:size).returns(0)

      iter = Iterator.new
      iter.expects(:hasNext).returns(false)

      set = Set.new
      set.expects(:iterator).returns(iter)

      map.expects(:entrySet).returns(set)

      assert_equals 0, HashMap.new(map).size
    end
  end

Mock Object Injection

James Mead — Thu, 29 Nov 2007 12:17:48 +0000

A few months back, in my Introduction to Mock Objects talk at LRUG, I talked about “Mock Object Injection”. At the time I described a number of different ways of replacing a production object with a Mock Object using Mocha. I remember that at the meeting, James Adam (who has since joined the team at Reevoo) asked me why I didn’t like the Any Instance Stub Injection technique.

I’m not sure I gave him a very convincing response and I’ve been meaning for ages to have a better go at explaining what I think are the pros and cons of each of the techniques I mentioned. Here’s the list of techniques with the ones I like best at the top. I still haven’t done a very good job, but I’d be interested to hear what other people think so that I can try and improve my understanding.

Constructor Injection

The ClassUnderTest allows its dependencies to be passed in as parameters to its constructor. A mock object is passed in as a replacement for the “real” collaborator. It may be convenient to specify the production collaborator as a default parameter value.

Advantages

The dependencies of the ClassUnderTest are explicit.

Disadvantages

Can’t think of any at the moment.

  class ClassUnderTest
    def initialize(dependency = Collaborator.new)
      @dependency = dependency
    end
    def do_something
      # use @dependency
    end
  end

  collaborator = mock('collaborator')
  # constructor parameter injection
  instance_under_test = ClassUnderTest.new(collaborator)
  instance_under_test.do_something

Parameter Injection

The ClassUnderTest allows its dependencies to be passed in as parameters to the method under test. A mock object is passed in as a replacement for the “real” collaborator. It may be convenient to specify the production collaborator as a default parameter value.

Advantages

The dependencies of the method under test are explicit.

Disadvantages

Can’t think of any at the moment.

  class ClassUnderTest
    def do_something(local_dependency = Collaborator.new)
      # use local_dependency
    end
  end

  collaborator = mock('collaborator')
  instance_under_test = ClassUnderTest.new
  # method parameter injection
  instance_under_test.do_something(collaborator)

Stubbed New Method Injection

Use Mocha’s Object#stubs to temporarily replace Collaborator#new with a stub implementation that returns a mock object.

Advantages

Better than Any Instance Stub Injection, because you can have more control over different instances of Collaborator.

Disadvantages

Dependencies of the ClassUnderTest are hidden and not explicit.

  class ClassUnderTest
    def initialize
      @dependency = Collaborator.new
    end
    def do_something
      # use @dependency
    end
  end

  collaborator = mock('collaborator')
  # stubbed new method injection
  Collaborator.stubs(:new).returns(collaborator)
  instance_under_test = ClassUnderTest.new
  instance_under_test.do_something

Writer Method Injection

Use an attribute writer method to replace the “real” collaborator with a mock object.

Disadvantages

The ClassUnderTest has to unnecessarily expose a way to modify its internal state. The test is coupled to the implementation of the ClassUnderTest.

  class ClassUnderTest
    attr_writer :dependency
    def initialize
      @dependency = Collaborator.new
    end
    def do_something
      # use @dependency
    end
  end

  collaborator = mock('collaborator')
  instance_under_test = ClassUnderTest.new
  # writer method injection
  instance_under_test.dependency = collaborator
  instance_under_test.do_something

Stubbed Private Method Injection

Use partial mocking to temporarily replace a private builder method with a stubbed version of the method.

Disadvantages

The test is coupled to the implementation of the ClassUnderTest. The partial mocking of the instance_under_test means that the test is not testing a pristine instance of the ClassUnderTest, but a modified one. It also means that the boundaries between test code and production code are less clear.

  class ClassUnderTest
    def do_something
      local_dependency = build_collaborator()
      # use local_dependency
    end
    private
    def build_collaborator
      Collaborator.new
    end
  end

  collaborator = mock('collaborator')
  instance_under_test = ClassUnderTest.new
  # stubbed private method injection
  instance_under_test.stubs(:build_collaborator).returns(collaborator)
  instance_under_test.do_something

Any Instance Stub Injection

Use Mocha’s Class#any_instance method to temporarily replace the method on a collaborator with a stub method.

Disadvantages

The stubbed method is applied to all instances of the collaborating class. If the instance_under_test interacts with the stubbed method on more than one instance of the collaborating class, it isn’t possible to specify different behaviour for the stubbed method on each instance. Even if the instance_under_test only interacts with the stubbed method on one instance of the collaborating class, the test is specifying more stubbed behaviour than strictly necessary which could lead to false positives.

  class ClassUnderTest
    def do_something
      local_dependency = Collaborator.new
      return local_dependency.do_stuff
    end
  end

  # any_instance stub injection
  Collaborator.any_instance.stubs(:do_stuff).return('something useful')
  instance_under_test = ClassUnderTest.new
  instance_under_test.do_something

Instance Variable Set Injection

Use Object#instance_variable_set to replace the reference to a collaborator with a mock object.

Disadvantages

The test is coupled to the implementation of the ClassUnderTest. In particular the test is coupled to the supposedly private instance variable. In my opinion, it would be more honest to expose the instance variable by adding an attribute writer and using Writer Method Injection.

  class ClassUnderTest
    def initialize
      @dependency = Collaborator.new
    end
    def do_something
      # use @dependency
    end
  end

  collaborator = mock('collaborator')
  instance_under_test = ClassUnderTest.new
  # instance_variable_set injection
  instance_under_test.instance_variable_set(:@dependency, collaborator)
  instance_under_test.do_something

Why Array#length is better than Array#size

James Mead — Tue, 07 Aug 2007 17:05:00 +0000

Recently Luke and I spotted a subtle bug in our code where we were mistakenly assuming a method returned an Array when it actually returned a Fixnum. We were then calling the #size method on the result, but interestingly Fixnum#size returns the number of bytes in its machine representation.

Previously I had noticed that my colleague Paul Battley tended to use Array#length in preference to Array#size. Now I know why, or at least I know why I’m going to start using Array#length! If we’d used #length in this case we would have seen a NoMethodError instead of the spurious value, 4.

  [5,6].size # => 2
  1.size # => 4
  [5,6].length # => 2
  1.length # => NoMethodError: undefined method `length' for 1:Fixnum

Update: Josh Susser has posted a useful related article about the use of…

Mock Objects in Ruby

James Mead — Sun, 22 Jul 2007 20:48:00 +0000

As promised I’ve finally got round to making the S5 slides of my LRUG talk available here.

You can use various keys to navigate the presentation. If you just want to quickly scan through the content, you might find the outline view useful (press the “T” key to toggle between slideshow & outline modes).

Mocha 0.5 released

James Mead — Fri, 08 Jun 2007 15:46:00 +0000

  sudo gem install mocha

or download one of the latest packages from rubyforge.

Parameter Matchers

I’ve added a few Hamcrest-style parameter matchers which are designed to be used inside Expectation#with. The following matchers are currently available: anything(), includes(), has_key(), has_value(), has_entry(), all_of() & any_of(). More to follow soon. The idea is eventually to get rid of the nasty parameter_block option on Expectation#with.

  object = mock()
  object.expects(:method).with(has_key('key_1'))
  object.method('key_1' => 1, 'key_2' => 2)
  # no verification error raised

  object = mock()
  object.expects(:method).with(has_key('key_1'))
  object.method('key_2' => 2)
  # verification error raised, because method was not called with Hash containing key: 'key_1'

Values Returned and Exceptions Raised on Consecutive Invocations

Allow multiple calls to Expectation#returns and Expectation#raises to build up a sequence of responses to invocations on the mock. Added syntactic sugar method Expectation#then to allow more readable expectations.

  object = mock()
  object.stubs(:method).returns(1, 2).then.raises(Exception).then.returns(4)
  object.method # => 1
  object.method # => 2
  object.method # => raises exception of class Exception
  object.method # => 4

Yields on Consecutive Invocations

Allow multiple calls to yields on single expectation to allow yield parameters to be specified for consecutive invocations.

  object = mock()
  object.stubs(:method).yields(1, 2).then.yields(3)
  object.method { |*values| p values } # => [1, 2]
  object.method { |*values| p values } # => [3]

Multiple Yields on Single Invocation

Added Expectation#multiple_yields to allow a mocked or stubbed method to yield multiple times for a single invocation.

  object = mock()
  object.stubs(:method).multiple_yields([1, 2], [3])
  object.method { |*values| p values } # => [1, 2] # => [3]

Invocation Dispatch

Expectations were already being matched in reverse order i.e. the most recently defined one was being found first. This is still the case, but we now stop matching an expectation when its maximum number of expected invocations is reached. c.f. JMock v1. A stub will never stop matching by default. Hopefully this means we can soon get rid of the need to pass a Proc to Expectation#returns.

  object = mock()
  object.stubs(:method).returns(2)
  object.expects(:method).once.returns(1)
  object.method # => 1
  object.method # => 2
  object.method # => 2
  # no verification error raised

This should still work…

  Time.stubs(:now).returns(Time.parse('Mon Jan 01 00:00:00 UTC 2007'))
  Time.now # => Mon Jan 01 00:00:00 UTC 2007
  Time.stubs(:now).returns(Time.parse('Thu Feb 01 00:00:00 UTC 2007'))
  Time.now # => Thu Feb 01 00:00:00 UTC 2007

Acknowledgements

Thanks to David Chelimsky, Dan North, Jay Fields, Kevin Clark, Frederick Cheung, James Moore, Brian Helmkamp, Ben Griffiths, Chris Roos & Paul Battley for their input. Apologies to anybody I forgot to mention.