Forum: RSpec should raise_error(ArgumentError) resulting in NoMethodError

Environment
------------------
ruby 1.9.2p0 (2010-08-18 revision 29036) [x86_64-darwin10.4.0]
rspec (1.3.0)

Code
-------
    def currency_to_dollars(currency_amount)
      raise ArgumentError("Currency amount can't be nil") if
currency_amount.nil?
    end

Spec
--------
    it "should raise an ArgumentError if currency_amount is nil" do
      lambda { @service.currency_to_dollars(nil) }.should
raise_error(ArgumentError)
    end

Results in this failure:
1)
'Service should raise an ArgumentError if currency_amount is nil' FAILED
expected ArgumentError, got #<NoMethodError: undefined method
`ArgumentError' for #<Service:0x0000010087e5f0>>
test/spec/service_spec.rb:92:in `block (2 levels) in <top (required)>'


Changing the test to either of these two variants allows the the to 
pass:

    lambda { @service.currency_to_dollars(nil) }.should
raise_error(StandardError)
    lambda { @service.currency_to_dollars(nil) }.should raise_error

Why am I unable to test for a specific StandardError subclass?

Thanks in advance for any help.
BP

FYI, the same thing happens with rspec 2.0.0.beta.20 as well:

  1) Service should raise an ArgumentError if currency_amount is nil
     Failure/Error: lambda
{ @service.currency_to_dollars(nil) }.should
raise_error(ArgumentError)
     expected ArgumentError, got #<NoMethodError: undefined method
`ArgumentError' for #<Service:0x000001029665d8>>
     # ./test/spec/service_spec.rb:92:in `block (2 levels) in <top
(required)>'

On Aug 25, 2010, at 10:13 PM, Brian Ploetz wrote:

> 
> Spec
> --------
>     it "should raise an ArgumentError if currency_amount is nil" do
>       lambda { @service.currency_to_dollars(nil) }.should raise_error(ArgumentError)
>     end
> 
> Results in this failure:
> 1)
> 'Service should raise an ArgumentError if currency_amount is nil' FAILED
> expected ArgumentError, got #<NoMethodError: undefined method `ArgumentError' for #<Service:0x0000010087e5f0>>

This message is telling you there is no ArgumentError method, not that 
the constant ArgumentError is missing. The method needs to be (adding 
".new"):

    def currency_to_dollars(currency_amount)
      raise ArgumentError.new("Currency amount can't be nil") if 
currency_amount.nil?
    end

> test/spec/service_spec.rb:92:in `block (2 levels) in <top (required)>'
> 
> 
> Changing the test to either of these two variants allows the the to pass:
> 
>     lambda { @service.currency_to_dollars(nil) }.should raise_error(StandardError)
>     lambda { @service.currency_to_dollars(nil) }.should raise_error

These pass because NoMethodError, which is what is being thrown, is a 
subclass of StandardError and Exception.

HTH,
David

On Aug 26, 2010, at 12:14 AM, David Chelimsky wrote:
>> currency_amount.nil?
>> 1)
>      raise ArgumentError.new("Currency amount can't be nil") if  
> currency_amount.nil?
>    end

You might see this form, too.

    def currency_to_dollars(currency_amount)
      raise ArgumentError, "Currency amount can't be nil" if
currency_amount.nil?
    end

Note the comma that separates the arguments to raise (Kernel#raise).

-Rob

>>    lambda { @service.currency_to_dollars(nil) }.should raise_error
>
> These pass because NoMethodError, which is what is being thrown, is  
> a subclass of StandardError and Exception.
>
> HTH,
> David
> _______________________________________________
> rspec-users mailing list
> rspec-users@rubyforge.org
> http://rubyforge.org/mailman/listinfo/rspec-users

Rob Biedenharn
Rob@AgileConsultingLLC.com  http://AgileConsultingLLC.com/
rab@GaslightSoftware.com    http://GaslightSoftware.com/

*smacks head* Duh.

Thanks David and Rob!


On Aug 26, 12:35 am, Rob Biedenharn <R...@AgileConsultingLLC.com>