numeric_near_matcher.rb

module Spec
  module Mocks
    # module ArgumentMatchers # rspec > 1.1.12
    module ArgumentConstraints

      # Based on:
      # http://trottercashion.com/2009/2/12/custom-argumentmatchers-in-rspec

      class NumericNearMatcher
        def initialize(expected, tolerance)
          @expected = expected
          @tolerance = tolerance
        end

        # actual is the value passed by the test. Its expected to respond to
        # between?, like that defined in Comparable, if not return false
        def ==(actual)
          actual.between?(@expected - @tolerance, @expected + @tolerance)
        rescue NoMethodError
          false
        end

        def description
          "numeric_near(#{@expected}, +/- #{@tolerance})"
        end
      end

      # This is the user interface that allows things like
      # obj.should_receive(:msg).with(a, numeric_near(1.23, 0.01))
      def numeric_near(*args)
        NumericNearMatcher.new(*args)
      end

    end
  end
end