Class: Propr::RSpecAdapter

Inherits:
Object show all
Defined in:
lib/propr/rspec.rb

Instance Method Summary collapse

Constructor Details

#initialize(group, options, property) ⇒ RSpecAdapter

Returns a new instance of RSpecAdapter.



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# File 'lib/propr/rspec.rb', line 4

def initialize(group, options, property)
  @options, @group, @property =
    options, group, property

  # Run each property 100 times, allow 50 retries, and
  # start the scale at 0, grow suddenly towards the end
  @runner = Runner.new(100, 50,
  # lambda{|p,s,t,_| (p+s <= t ? p+s : t) / t })
    lambda{|p,s,t,_| (BigDecimal(p+s <= t ? p+s : t) / t) })
end

Instance Method Details

#check(*args, &generator) ⇒ Object 



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# File 'lib/propr/rspec.rb', line 15

def check(*args, &generator)
  m        = self
  runner   = @runner
  property = @property

  if block_given?
    location = location(generator)

    @group.example(@property.name, @options.merge(caller: location)) do
      success, passed, skipped, counterex =
        runner.run(property, generator)

      unless success
        if skipped >= runner.maxskip
          raise NoMoreTries.new(runner.maxskip), nil, location
        else
          raise Falsifiable.new(counterex, m.shrink(counterex), passed, skipped), nil, location
        end
      end
    end
  else
    location = location(caller)

    @group.example(@property.name, @options.merge(caller: location)) do
      unless property.call(*args)
        raise Falsifiable.new(args, m.shrink(args), 0, 0), nil, location
      end
    end
  end

  # Return `self` to allow chaining calls to `check`
  self
end

#shrink(counterex) ⇒ Object

TODO: this method is not RSpec specific



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# File 'lib/propr/rspec.rb', line 50

def shrink(counterex)
  if @property.arity.zero?
    return []
  end

  xs = [counterex]

  while true
    # Generate simpler examples
    ys = Array.bind(xs) do |args|
      head, *tail = args.map{|x| x.respond_to?(:shrink) ? x.shrink : [x] }
      head.product(*tail)
    end

    zs = []

    # Collect counter examples
    until ys.empty? or zs.length >= 10
      args = ys.delete_at(rand(ys.size))

      unless @property.call(*args)
        zs.push(args)
      end
    end

    if zs.empty?
      # No simpler counter examples
      return xs.first
    else
      # Try to further simplify these
      xs = zs
    end
  end
end