Mocha matcher to recursively match nested data structures

partial_object.rb

require 'mocha/parameter_matchers/base'

module Mocha
  module ParameterMatchers
    # @example
    #   partial = {
    #     a: [ 1, 2 ],
    #     b: {
    #       hello: {
    #         world: [ 'foo' ]
    #       }
    #     }
    #   }
    #
    #   full = {
    #     a: [ 1, 2, 3 ],
    #     b: {
    #       hello: {
    #         world: [ 'foo', 'bar' ]
    #       }
    #     },
    #     c: 'baz'
    #   }
    #
    #   object = mock()
    #   object.expects(:method_1).with(partial_object(partial))
    #   object.method_1(full)
    #   # no error raised
    def partial_object(o)
      PartialObject.new(o)
    end

    class PartialObject < ::Mocha::ParameterMatchers::Base
      def initialize(partial)
        @partial = partial
      end

      def matches?(available_parameters)
        _matches?(@partial, available_parameters.shift)
      end

      def _matches?(partial, other)
        case partial
        when ::Mocha::ParameterMatchers::Base
          partial.matches?(other)
        when Hash
          partial.all? { |k, v| other.has_key?(k) && _matches?(v, other[k]) }
        when Enumerable
          partial.zip(other).all? { |a, b| _matches?(a, b) }
        else
          partial == other
        end
      end

      def mocha_inspect
        "partial_object(#{@partial.mocha_inspect})"
      end
    end
  end
end