weird_error.rb

require "test/unit"
require "rubygems"
require "shoulda"
require "mocha"

class Red
  def gets(*args)
    @input.gets(*args)
  end
  def puts(*args)
    @output.puts(*args)
  end
  def initialize
    @input = $stdin
    @output = $stdout
  end
  private
  def first_method
    input = gets.chomp
    if input == "test"
      second_method(input)
    end
  end
  def second_method(value)
    puts value
    # second_method(value) # this would result in infinite recursion
  end
end

class FooTest < Test::Unit::TestCase
  context "foo" do
    setup do
      @project = Red.new
      @project.instance_variable_set(:@input, StringIO.new("test\n"))
      @project.stubs(:second_method)
    end
    should "pass input value to second_method" do
      @project.expects(:second_method).with("test").once
      @project.instance_eval {first_method}
    end
  end
end

$ ruby Desktop/weird_error.rb 
Loaded suite Desktop/weird_error
Started
.
Finished in 0.000811 seconds.

1 tests, 1 assertions, 0 failures, 0 errors

If I comment out line #21 i.e. the call to Red#second_method from within Red#first_method, I get the test failure I would expect :-

$ ruby Desktop/weird_error.rb
Loaded suite Desktop/weird_error
Started
F
Finished in 0.0094 seconds.

  1) Failure:
test: foo should pass input value to second_method. (FooTest)
    [Desktop/weird_error.rb:38:in `__bind_1291295490_929583'
     /Users/jamesmead/.rvm/gems/ree-1.8.7-2010.02/gems/shoulda-2.11.3/lib/shoulda/context.rb:382:in `call'
     /Users/jamesmead/.rvm/gems/ree-1.8.7-2010.02/gems/shoulda-2.11.3/lib/shoulda/context.rb:382:in `test: foo should pass input value to second_method. ']:
not all expectations were satisfied
unsatisfied expectations:
- expected exactly once, not yet invoked: #<Red:0x101705ab0>.second_method('test')
satisfied expectations:
- allowed any number of times, not yet invoked: #<Red:0x101705ab0>.second_method(any_parameters)

1 tests, 1 assertions, 1 failures, 0 errors

$ ruby -v
ruby 1.8.7 (2010-04-19 patchlevel 253) [i686-darwin10.4.0], MBARI 0x6770, Ruby Enterprise Edition 2010.02
$ gem -v
1.3.7
$ gem list mocha

*** LOCAL GEMS ***

mocha (0.9.10)
$ gem list shoulda

*** LOCAL GEMS ***

shoulda (2.11.3)