From: Jacob Fugal <lukfugl@...>
Date: 2006-05-13T00:45:02+09:00
Subject: Re: Unit testing with mock objects

On 5/11/06, Dido Sevilla <dido.sevilla@gmail.com> wrote:
> class Foo
>   def initialize(x, y, &block)
>     if block_given?
>       dobjs = block.call
>       @domain_obj1 = dobjs[:domain_obj1]
>       @domain_obj2 = dobjs[:domain_obj2]
>     else
>       @domain_obj1 = DomainObj1.new
>       @domain_obj2 = DomainObj2.new
>     end
>   end
>
> so that in my testing code I can do the following:
>
> FlexMock.use("domain_obj1") do |dobj1|
>   FlexMock.use("domain_obj2").do |dobj2|
>     f = Foo.new(x, y) { {:domain_obj1 => dobj1, :domain_obj2 => dobj2 } }
>   end
> end

I like the "trailing option hash" "pattern" (used loosely). It's
pretty close to what you've got, but syntactlcally a little nicer. I'd
do it like this for your demonstrated class:

  class Foo
    DEFAULTS = {
      :domain_obj1 => DomainObj1,
      :domain_obj2 => DomainObj2
    }

    def initialize(x, y, options={})
      options.merge!(DEFAULTS)
      @domain_obj1 = options[:domain_obj1]
      @domain_obj2 = options[:domain_obj2]
      @domain_obj1 = @domain_obj1.new if Class === @domain_obj1
      @domain_obj2 = @domain_obj2.new if Class === @domain_obj2
    end
  end

I use the classes in the DEFAULTS array so that each instance of Foo
can have it's own DomainObj1 (in the default case), rather than having
a reference to the same object that was instantiated when the hash was
created. The "x = x.new if Class === x" "pattern" (again, loosely
using the P word) is also useful in that you can pass in a MockClass
as well, rather than an instantiated object, if you want. Example
usage:

  # passing mock objects
  FlexMock.use("domain_obj1") do |dobj1|
    FlexMock.use("domain_obj2").do |dobj2|
      f = Foo.new(x, y,
        :domain_obj1 => dobj1,
        :domain_obj2 => dobj2)
    end
  end

--OR--

  # passing mock classes
  f = Foo.new(x, y,
    :domain_obj1 => MockDomainObj1,
    :domain_obj2 => MockDomainObj2)

--OR--

  # normal, non-test usage, should look same as before:
  f = Foo.new(x, y)

How's that look?

Jacob Fugal