PragmaticGP_pile5.feature

Feature: One-point uneven crossover works as specified
  In order to combine "good ideas" that have arisen independently in different Pile scripts
  As a symbolic regression modeler
  I want crossover to snip scripts up and stick them back together

  Scenario: crossover conserves the number of tokens
    Given parent_1 is the Pile script "+ + + + + + + + + +"
    And parent_2 is the Pile script "- - - - - - - - - -"
    When I apply uneven one-point crossover to those parents
    Then the result is a collection of 2 Pile scripts
    And there should be 20 tokens altogether in the offspring
    And the pooled tokens from both offspring should include 10 "+"
    And the pooled tokens from both offspring should include 10 "-"

  Scenario: crossover breakpoints are chosen with uniform probability
    Given parent_1 is the Pile script "+ + + + + + + + + +"
    And parent_2 is the Pile script "- - - - - - - - - -"
    When I apply crossover to those parents (independently) many times
    Then the minimum length of an offspring should be 0 tokens
    And the maximum length of an offspring should be 20 tokens