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Mutation testing with the mutant gem

DonSchado
DonSchado

The document discusses mutation testing in software development, which evaluates the quality of existing tests by introducing small changes (mutations) to the code. It explains how mutants are created, detected, and how projects can achieve high mutation coverage using the 'mutant' gem. Additionally, it includes examples of sorting algorithms implemented in Ruby and instructions for using the mutant tool with RSpec.

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Mutation Testing @DonSchado cologne.rb | 16.10.2013
disclaimer This presentation contains: - memes a definition lots of screenshots overdrawn code examples a short quiz time surviving mutants no ponies
def mutation_testing     <<-eos     is used to evaluate the quality of existing software tests     modifying the program's source code based on well-defined mutation operators        each 'mutated' version is called a mutant        a test which detects the mutation (fail) will kill the mutant        mutants without failing tests are alive     eos  end
def mutation_testing     <<-eos     is used to evaluate the quality of existing software tests     modifying the program's source code based on well-defined mutation operators        each 'mutated' version is called a mutant        a test which detects the mutation (fail) will kill the mutant        mutants without failing tests are ALIVE     eos  end
gem 'mutant', '~> 0.3.0.rc3'
Mutation testing with the mutant gem
Projects using Mutant The following projects adopted mutant, and aim 100% mutation coverage: • • • • • • • • • axiom axiom-types rom-mapper rom-session event_bus virtus quacky substation large_binomials
Mutation testing with the mutant gem
Mutation testing with the mutant gem
source "https://rubygems.org"     gem 'simplecov', "~> 0.8.0.pre2"  gem "rake", "~> 10.1.0" gem "rspec", "~> 2.14.0" gem "mutant", "~> 0.3.0.rc3" gem "rspec-pride", "~> 2.2.0", :require => false gem "activesupport", "~> 4.0.0", :require => false
require 'spec_helper'   describe 'FancyAlgorithm' do     let(:random_list) { %w[2 1 3 5 6 4 9 8 7] }   let(:sorted_list) { %w[1 2 3 4 5 6 7 8 9] }   context ':sort' do     subject { FancyAlgorithm.new(:sort) }     it { expect(subject.perform(random_list)).to eql(sorted_list) }   end   context ':unsort' do     subject { FancyAlgorithm.new(:unsort) }     it { expect(subject.perform(random_list)).to_not eql(sorted_list) }   end end
class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end
class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private This is obviously more advanced than Array#sort.     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private Quiztime: Which sorting algorithm is this?     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private Quiztime: What‘s the average Big-O complexity of this sorting algorithm?     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private Quiztime: What‘s the sorting algorithm behind Ruby‘s Array#sort?     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
Mutation testing with the mutant gem
$ mutant --help usage: mutant STRATEGY [options] MATCHERS ... Strategies: --rspec --rspec-level LEVEL --ignore-subject MATCHER --zombie -I, --include DIRECTORY -r, --require NAME Options: --version --code FILTER --fail-fast -d, --debug -h, --help kills mutations with rspec set rspec expansion level ignores subjects that matches MATCHER Run mutant zombified Add DIRECTORY to $LOAD_PATH Require file with NAME Print mutants version Adds a code filter Fail fast Enable debugging output Show this message
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm#initialize
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm#initialize Mutant configuration: Matcher: #<Mutant::Matcher::Method::Instance cache=#<Mutant::Cache> scope=FancyAlgorithm method=#<UnboundMethod: FancyAlgorithm#initialize>> Subject Filter: Mutant::Predicate::CONTRADICTION Strategy: #<Mutant::Strategy::Rspec level=0> FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.79s FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 evil:FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4:b34d0 @@ -1,4 +1,4 @@ def initialize(strategy) - @strategy = strategy.to_s + @strategy = strategy end (09/10) 90% - 0.79s Subjects: 1 Mutations: 10 Kills: 9 Runtime: 0.86s Killtime: 0.79s Overhead: 8.84% Coverage: 90.00% Alive: 1
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm#initialize Mutant configuration: Matcher: #<Mutant::Matcher::Method::Instance cache=#<Mutant::Cache> scope=FancyAlgorithm method=#<UnboundMethod: FancyAlgorithm#initialize>> Subject Filter: Mutant::Predicate::CONTRADICTION Strategy: #<Mutant::Strategy::Rspec level=0> FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.79s FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 evil:FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4:b34d0 @@ -1,4 +1,4 @@ def initialize(strategy) - @strategy = strategy.to_s def initialize(strategy) + @strategy = strategy     @strategy = strategy.to_s end   end (09/10) 90% - 0.79s Subjects: 1 def perform(list) Mutations: 10     self.send("#{strategy}_algorithm!", list) Kills: 9   end Runtime: 0.86s Killtime: 0.79s Overhead: 8.84% Coverage: 90.00% Alive: 1 implicit!
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.80s FancyAlgorithm#perform:/../lib/fancy_algorithm.rb:8 .......F.......... (17/18) 94% - 1.44s FancyAlgorithm#sort_algorithm!:/../lib/fancy_algorithm.rb:14 ...........FFF.F..FFFFF.........................F........ (47/57) 82% - 4.87s FancyAlgorithm#unsort_algorithm!:/../lib/fancy_algorithm.rb:27 ....FF.FFFFFFF.FFF (06/18) 33% - 1.52s Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.80s FancyAlgorithm#perform:/../lib/fancy_algorithm.rb:8 .......F.......... (17/18) 94% - 1.44s FancyAlgorithm#sort_algorithm!:/../lib/fancy_algorithm.rb:14 ...........FFF.F..FFFFF.........................F........ (47/57) 82% - 4.87s FancyAlgorithm#unsort_algorithm!:/../lib/fancy_algorithm.rb:27 ....FF.FFFFFFF.FFF (06/18) 33% - 1.52s Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... self.send("#{strategy}_algorithm!", list) def perform(list) + send("#{strategy}_algorithm!", list)     self.send("#{strategy}_algorithm!", list)   end Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 + if list.size <= 1 if list.size <= 2 Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 + if list.size <= 1 if list.size <= 2 + if list.size <= 1 if list.size <= nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 + if list.size <= 1 if list.size <= 2 + if list.size <= 1 if list.size <= nil + if list.size <= 1 if list.size <= false Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list) + return(nil) Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list) + return(nil) + if list.size <= 1 return(list) end nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list) + return(nil) + if list.size <= 1 return(list) end nil - if list.size <= 1 return(list) end Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil + unless list.empty? unless !list.emtpy? Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil + unless list.empty? unless !list.emtpy? + unless list.empty? unless false Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil + unless list.empty? unless !list.emtpy? + unless list.empty? unless false + unless list.empty? if list.empty? Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) + return(list.shuffle) list.shuffle Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) + return(list.shuffle) list.shuffle + return(list.shuffle) return(nil) Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
$ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) + return(list.shuffle) list.shuffle + return(list.shuffle) return(nil) + unless list.empty? return(list.shuffle) end nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
- Try it by yourself clone the repo play around write specs to kill the mutants run mutant in other projects create issues help improve the documentation mutate all the things
example project (including this slides): https://github.com/DonSchado/colognerb-on-mutant in addition: https://github.com/DonSchado/bob-the-mutant obviously: https://github.com/mbj/mutant for reference: http://slid.es/markusschirp/mutation-testing/ http://solnic.eu/2013/01/23/mutation-testing-with-mutant.html rails? https://github.com/mockdeep/mutant-rails

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Mutation testing with the mutant gem

  • 2. disclaimer This presentation contains: - memes a definition lots of screenshots overdrawn code examples a short quiz time surviving mutants no ponies
  • 3. def mutation_testing     <<-eos     is used to evaluate the quality of existing software tests     modifying the program's source code based on well-defined mutation operators        each 'mutated' version is called a mutant        a test which detects the mutation (fail) will kill the mutant        mutants without failing tests are alive     eos  end
  • 4. def mutation_testing     <<-eos     is used to evaluate the quality of existing software tests     modifying the program's source code based on well-defined mutation operators        each 'mutated' version is called a mutant        a test which detects the mutation (fail) will kill the mutant        mutants without failing tests are ALIVE     eos  end
  • 5. gem 'mutant', '~> 0.3.0.rc3'
  • 7. Projects using Mutant The following projects adopted mutant, and aim 100% mutation coverage: • • • • • • • • • axiom axiom-types rom-mapper rom-session event_bus virtus quacky substation large_binomials
  • 10. source "https://rubygems.org"     gem 'simplecov', "~> 0.8.0.pre2"  gem "rake", "~> 10.1.0" gem "rspec", "~> 2.14.0" gem "mutant", "~> 0.3.0.rc3" gem "rspec-pride", "~> 2.2.0", :require => false gem "activesupport", "~> 4.0.0", :require => false
  • 11. require 'spec_helper'   describe 'FancyAlgorithm' do     let(:random_list) { %w[2 1 3 5 6 4 9 8 7] }   let(:sorted_list) { %w[1 2 3 4 5 6 7 8 9] }   context ':sort' do     subject { FancyAlgorithm.new(:sort) }     it { expect(subject.perform(random_list)).to eql(sorted_list) }   end   context ':unsort' do     subject { FancyAlgorithm.new(:unsort) }     it { expect(subject.perform(random_list)).to_not eql(sorted_list) }   end end
  • 12. class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end
  • 13. class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private This is obviously more advanced than Array#sort.     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
  • 14. class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private Quiztime: Which sorting algorithm is this?     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
  • 15. class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private Quiztime: What‘s the average Big-O complexity of this sorting algorithm?     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
  • 16. class FancyAlgorithm   attr_accessor :strategy   def initialize(strategy)     @strategy = strategy.to_s   end   def perform(list)     self.send("#{strategy}_algorithm!", list)   end   private Quiztime: What‘s the sorting algorithm behind Ruby‘s Array#sort?     def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end       def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  end http://bigocheatsheet.com/ http://www.igvita.com/2009/03/26/ruby-algorithms-sorting-trie-heaps/
  • 18. $ mutant --help usage: mutant STRATEGY [options] MATCHERS ... Strategies: --rspec --rspec-level LEVEL --ignore-subject MATCHER --zombie -I, --include DIRECTORY -r, --require NAME Options: --version --code FILTER --fail-fast -d, --debug -h, --help kills mutations with rspec set rspec expansion level ignores subjects that matches MATCHER Run mutant zombified Add DIRECTORY to $LOAD_PATH Require file with NAME Print mutants version Adds a code filter Fail fast Enable debugging output Show this message
  • 19. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm#initialize
  • 20. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm#initialize Mutant configuration: Matcher: #<Mutant::Matcher::Method::Instance cache=#<Mutant::Cache> scope=FancyAlgorithm method=#<UnboundMethod: FancyAlgorithm#initialize>> Subject Filter: Mutant::Predicate::CONTRADICTION Strategy: #<Mutant::Strategy::Rspec level=0> FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.79s FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 evil:FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4:b34d0 @@ -1,4 +1,4 @@ def initialize(strategy) - @strategy = strategy.to_s + @strategy = strategy end (09/10) 90% - 0.79s Subjects: 1 Mutations: 10 Kills: 9 Runtime: 0.86s Killtime: 0.79s Overhead: 8.84% Coverage: 90.00% Alive: 1
  • 21. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm#initialize Mutant configuration: Matcher: #<Mutant::Matcher::Method::Instance cache=#<Mutant::Cache> scope=FancyAlgorithm method=#<UnboundMethod: FancyAlgorithm#initialize>> Subject Filter: Mutant::Predicate::CONTRADICTION Strategy: #<Mutant::Strategy::Rspec level=0> FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.79s FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 evil:FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4:b34d0 @@ -1,4 +1,4 @@ def initialize(strategy) - @strategy = strategy.to_s def initialize(strategy) + @strategy = strategy     @strategy = strategy.to_s end   end (09/10) 90% - 0.79s Subjects: 1 def perform(list) Mutations: 10     self.send("#{strategy}_algorithm!", list) Kills: 9   end Runtime: 0.86s Killtime: 0.79s Overhead: 8.84% Coverage: 90.00% Alive: 1 implicit!
  • 22. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm
  • 23. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.80s FancyAlgorithm#perform:/../lib/fancy_algorithm.rb:8 .......F.......... (17/18) 94% - 1.44s FancyAlgorithm#sort_algorithm!:/../lib/fancy_algorithm.rb:14 ...........FFF.F..FFFFF.........................F........ (47/57) 82% - 4.87s FancyAlgorithm#unsort_algorithm!:/../lib/fancy_algorithm.rb:27 ....FF.FFFFFFF.FFF (06/18) 33% - 1.52s Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
  • 24. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... FancyAlgorithm#initialize:/../lib/fancy_algorithm.rb:4 ......F... (09/10) 90% - 0.80s FancyAlgorithm#perform:/../lib/fancy_algorithm.rb:8 .......F.......... (17/18) 94% - 1.44s FancyAlgorithm#sort_algorithm!:/../lib/fancy_algorithm.rb:14 ...........FFF.F..FFFFF.........................F........ (47/57) 82% - 4.87s FancyAlgorithm#unsort_algorithm!:/../lib/fancy_algorithm.rb:27 ....FF.FFFFFFF.FFF (06/18) 33% - 1.52s Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
  • 25. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... self.send("#{strategy}_algorithm!", list) def perform(list) + send("#{strategy}_algorithm!", list)     self.send("#{strategy}_algorithm!", list)   end Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
  • 26. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 27. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 28. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 + if list.size <= 1 if list.size <= 2 Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 29. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 + if list.size <= 1 if list.size <= 2 + if list.size <= 1 if list.size <= nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 30. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... if list.size <= 1 + if list.size <= -1 + if list.size <= 1 if list.size <= 2 + if list.size <= 1 if list.size <= nil + if list.size <= 1 if list.size <= false Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 31. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list) + return(nil) Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 32. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list) + return(nil) + if list.size <= 1 return(list) end nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 33. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list) + return(nil) + if list.size <= 1 return(list) end nil - if list.size <= 1 return(list) end Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def sort_algorithm!(list)       return list if list.size <= 1       0.upto(list.size - 1) do |i|         (list.size - 1).downto(i + 1) do |j|           if list[j] < list[j - 1]             list[j], list[j - 1] = list[j - 1], list[j]           end          end       end       list      end
  • 34. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end  Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24
  • 35. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 36. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil + unless list.empty? unless !list.emtpy? Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 37. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil + unless list.empty? unless !list.emtpy? + unless list.empty? unless false Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 38. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... unless list.empty? + unless nil + unless list.empty? unless !list.emtpy? + unless list.empty? unless false + unless list.empty? if list.empty? Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 39. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 40. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) + return(list.shuffle) list.shuffle Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 41. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) + return(list.shuffle) list.shuffle + return(list.shuffle) return(nil) Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 42. $ mutant --rspec -I lib -r fancy_algorithm FancyAlgorithm Mutant configuration: ... return(list.shuffle) + return(list) + return(list.shuffle) list.shuffle + return(list.shuffle) return(nil) + unless list.empty? return(list.shuffle) end nil Subjects: Mutations: Kills: Runtime: Killtime: Overhead: Coverage: Alive: 4 103 79 9.46s 8.62s 8.84% 76.70% 24 def unsort_algorithm!(list)       return list.shuffle unless list.empty?     end 
  • 43. - Try it by yourself clone the repo play around write specs to kill the mutants run mutant in other projects create issues help improve the documentation mutate all the things
  • 44. example project (including this slides): https://github.com/DonSchado/colognerb-on-mutant in addition: https://github.com/DonSchado/bob-the-mutant obviously: https://github.com/mbj/mutant for reference: http://slid.es/markusschirp/mutation-testing/ http://solnic.eu/2013/01/23/mutation-testing-with-mutant.html rails? https://github.com/mockdeep/mutant-rails