[rspec-devel] [ rspec-Bugs-12845 ] Typo when using instance variables in specs leads to setting expectations on the nil object

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Bugs item #12845, was opened at 2007-08-06 11:04
You can respond by visiting: 
http://rubyforge.org/tracker/?func=detail&atid=3149&aid=12845&group_id=797

Category: mock module
Group: None
Status: Open
Resolution: None
Priority: 3
Submitted By: Ashley Moran (ashley_moran)
Assigned to: Nobody (None)
Summary: Typo when using instance variables in specs leads to setting expectations on the nil object

Initial Comment:
Just spent ages bashing my head against a wall on this, wondering why my spec was failing.  Basically summed up in this example (not the shortest but similar to my code):

class Computer
  attr_reader :power_indicator
  
  def initialize(power_indicator)
    @power_indicator = power_indicator
  end
  
  def turn_off
    power_indicator.dim
  end
end

describe Computer, "created with a PowerIndicator" do
  before(:each) do
    @power_indicator = mock("PowerIndicator")
    @computer = Computer.new(@power_indicator)
  end
  
  it "should dim the power indicator when sent :turn_off" do
    @power_indciator.should_receive(:dim)
    @computer.turn_off
  end
end

Basically I don't see a reason why you would ever set an expectation on "nil", so I wondered, would the following be better behaviour?

describe NilClass do
  it "should raise an exception when sent :should_receive" do
    lambda { nil.should_receive(:some_message) }.should raise_error(StandardError)
  end
end

A bit like the way when you do "nil.id" in ActiveRecord you get the warning about calling nil.id in case you meant nil.object_id.  WDYT?

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