         .to.deep.equal [1, 1, 1, 1]
       expect offspring.fitness()
         .to.equal 4
+
+    it 'should not work if not enough probability', ->
+      pair.mutate 0, ->
+        throw new AssertionError 'mutation operator should not call'

'use strict'
{expect, assert} = require 'chai'

describe 'Individual.pair', ->
  Popuration = require '../lib/popuration'


      it 'should contains clone of parents if not enough probability', ->
        pair.crossover 0, ->
          throw new AssertionError 'crossover operator should not call'

        expect pair.offsprings
          .to.be.a 'array'
