Question

I wonder if there’s any good way to reuse data between implementation and description of a spec… More particularly, I’d like to be able do something like the following:

describe "#some_method" do
  let(:arg1) { "Sample String 1" }
  let(:arg2) { "Sample String 2" }

  context "with '#{arg1}', its result" do
    specify { some_method(arg1).should == 1 }
  end

  context "with '#{arg2}', its result" do
    specify { some_method(arg2).should == 2 }
  end
end

Of course, this code won’t work – arg1 and arg2 are not accessible outside of spec bodies.
Is it possible to achieve the similar result without using global variables or external classes?

Update:

I’m interested in the output of the spec. Something like this:

#some_method
  with 'Sample String 1' its result
    should == 1
  with 'Sample String 2' its result
    should == 2

Answer 1

The answer is that you don’t use dynamic descriptions. The RSpec way to do this would be

describe "#some_method" do
  it "extracts the number correctly" do
    some_method("Sample String 1").should == 1
    some_method("Sample String 2").should == 2
  end
end

It is no problem to hard-code test data in your specs. If you want more complete output, you can use a custom matcher

require 'rspec'

class Test
  def some_method(str)
    str[/[0-9]+/].to_i
  end
end

RSpec::Matchers.define :return_value_for_argument do |result, arg|
  match do |actual|
    actual.call(arg) == result
  end

  description do
    "return #{result.inspect} for argument #{arg.inspect}"
  end
end

describe Test do
  let(:test) { Test.new }
  describe "#some_method" do
    subject { test.method(:some_method) }

    it { should return_value_for_argument 1, "str 1" }
  end
end