Not able to understand how the method subject! does work

[Arup Rakshit]

#######

test.rb

#######

#!/usr/bin/env ruby

class Thing

  def self.count

    @count ||= 0

  end

  def self.count=(val)

    @count += val

  end

  def self.reset_count

    @count = 0

  end

  def initialize

    self.class.count += 1

  end

end

###########

test_spec.rb

###########

require_relative "../test.rb"

describe Thing do

  after(:example) do

    puts "called" 

    #Thing.reset_count

  end

  context "using subject!" do

    subject!(:thing) { Thing.new }

    it "returns 1" do

      expect(Thing.count).to eq(1)

    end

    it "returns 2" do

      expect(Thing.count).to eq(2)

    end

  end

end

If I run the test :-

arup@linux-wzza:~/Ruby> rspec spec/test_spec.rb

.F

Failures:

  1) Thing using subject! returns memoized version on first invocation

     Failure/Error: expect(Thing.count).to eq(1)

       expected: 1

            got: 3

       (compared using ==)

     # ./spec/test_spec.rb:13:in `block (3 levels) in <top (required)>'

Finished in 0.00173 seconds (files took 0.13718 seconds to load)

2 examples, 1 failure

Failed examples:

rspec ./spec/test_spec.rb:11 # Thing using subject! returns memoized version on first invocation

Now my question is how @count incremented by 3, shouldn't it be by 2 ?

[Surya]

I think subject() defines the value which will be returned by the subject method: https://www.relishapp.com/rspec/rspec-core/v/2-6/docs/subject/explicit-subject

context "using subject!" do

    subject { Thing.new }

    it "returns 1" do

      expect(subject.class.count).to eq(1)

    end

end

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Regards,
Surya

[Aaron Kromer]

You have a typo in your Thing code:

  def self.count=(val)
    # Typo is +=, use just =
    @count += val
  end

That should just be @count = val not +=. This is causing count to increase in size each time by 1 plus itself.

To view this discussion on the web visit https://groups.google.com/d/msgid/rspec/CAHGOqz489cB6o00nC7NKfa5%3DoMKXwirRPDpffM6%2BsbsFip2-xg%40mail.gmail.com.

[Arup Rakshit]

Hello Aaron,

Thanks... Late night reading might causes it.. :-) Thanks for your help.