The hitchhicker’s guide to unit testing

You already know TDD, your code coverage is almost at 80%, jUnit has no secret for you? But you feel that you could do more with your tests, the tools you use have limitations. Or maybe you're just tired of assertEquals?

Don't panic! We will see how you can code tests. We will look upon:

- Mutation Testing
- BDD, Behaviour Driven Development
- Property Testing

Transcript

1. The  hitchhicker’s  
   guide  to  unit  tes1ng  
   Rémy-­‐Christophe  Schermesser  
   @el_picador  
   

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2. Ruby!  
   Scala!  
   Java!  
   Python!  
   PHP!  
   

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3. Ruby!  
   Scala!  
   Java!  
   Python!  
   PHP!  
   But  don’t  forget  your  towel  
   

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4. Test::Unit  
   ScalaTest  
   jUnit  
   uniFest  
   PHPUnit  
   

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5. Test::Unit  
   ScalaTest  
   jUnit  
   uniFest  
   PHPUnit  
   Again  don’t  forget  your  towel  
   

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6. JUnit
    
   

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7. assertEquals  
   At  the  beginning,  we  had  
   

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8. Then  
   assertThatMyTestFitsOn
   OneLine(whatIExpect,  
   whatMyCodeIsDoing);  
   

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9. And  
   void  testWithCamelCase
   ToReadItBeFer()  {  ...  }  
   

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10. And  again  
    @Test  
    void  annotaZonsAreGood
    ForYourHealth()  {  ...  }  
    

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11. And  again  again  
    void  testMyTest()  {    
     Obj  obj  =  new  Obj();  
     //  10  lignes  of  things  
     assertEquals(…);  
    }  
    

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12. JUnit
     
    

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13. JUnit
     
    Mocks
     
    

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14. JUnit
     
    Fixtures
     
    Mocks
     
    

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15. JUnit
     
    Behavior
     
    tes1ng
     
    with
     
    RSpec
     
    

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16. Problem  
    void  testMyTest()  {    
     Obj  obj  =  new  Obj();  
     //  10  lignes  of  things  
     assertEquals(…);  
    }  
    

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17. Behavior  tesZng,  don’t  test,  do  describe
     
    Describe  what  
    your  program  
    should  do  
    

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18. One  test  
    One  (english)  
    sentence  
    Behavior  tesZng,  don’t  test,  do  describe
     
    

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19. RSpec,  don’t  panic,
     
    factorize  and  do  DSL
     
    

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20. describe  CompaniesController  do  
         describe  "POST  create"  do  
               context  "when  recruiter    
    signed_in  with  no  company"  do
     
                     …  
               end  
         end  
    end  
    

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21. describe  CompaniesController  do  
         describe  "POST  create"  do  
               context  "when  recruiter    
    signed_in  with  no  company"  do
     
                     …  
               end  
         end  
    end  
    

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22. describe  CompaniesController  do  
         describe  "POST  create"  do  
               context  "when  recruiter    
    signed_in  with  no  company  an  email  is
     
    sent"  do
     
                     …  
               end  
         end  
    end  
    

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23. let!(:recruiter)  {  login_recruiter  create(:recruiter,      
               company_id:  nil)  }  
       
    context  "when  good  params"  do  
     let(:params)  {  …  }  
       
       it  {  expect  {  post  :create,  params  }.to  change(Company,  :count).by  1  }  
       it  {  expect  {  post  :create,  params  }.to  
           change(Ac1onMailer::Base.deliveries,  :count).by  2  }  
     
    end  
    “When  recruiter  signed_in  with  no  company”
    
    

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24. let!(:recruiter)  {  login_recruiter  create(:recruiter,  company_id:  nil)  }  
       
    context  "when  good  params"  do  
     let(:params)  {  …  }  
       
       it  {  expect  {  post  :create,  params  }.to  change(Company,  :count).by  1  }  
       it  {  expect  {  post  :create,  params  }.to  
           change(Ac1onMailer::Base.deliveries,  :count).by  2  }  
     
    end  
    “When  recruiter  signed_in  with  no  company”
    
    

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25. let!(:recruiter)  {  login_recruiter  create(:recruiter,  company_id:  nil)  }  
       
    context  "when  good  params"  do  
     let(:params)  {  …  }  
       
       it  {  expect  {  post  :create,  params  }.to  change(Company,  :count).by  1  }  
       it  {  expect  {  post  :create,  params  }.to  
           change(Ac1onMailer::Base.deliveries,  :count).by  2  }  
     
    end  
    “When  recruiter  signed_in  with  no  company”
    
    

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26. let!(:recruiter)  {  login_recruiter  create(:recruiter,  company_id:  nil)  }  
       
    context  "when  good  params"  do  
     let(:params)  {  …  }  
       
       it  {  expect  {  post  :create,  params  }.to        
             change(Company,  :count).by  1  }  
       it  {  expect  {  post  :create,  params  }.to        
         change(Ac1onMailer::Base.deliveries,  :count).by  2  }  
     
    end  
    “When  recruiter  signed_in  with  no  company”
    
    

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27. Like  a  towel,  use  it  every  day  
    

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28. JUnit
     
    Muta1on  
    tes1ng
     
    Behavior
     
    tes1ng
     
    with
     
    Javalanche
     
    

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29. Code  coverage  
    has  limits
     
    Code:  ctrl+c
     
    Test:  ctrl+v
     
    

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30. Code  a  class  and  test  it  
    

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31. Mutate  it  
    

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32. &&
     
    ++
     
    !=
     
    >
     
    …
     
    ||
     
    -­‐-­‐
     
    ==
     
    <
     
    …
     
    Mutate  it  
    

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33. if(a  &&  b)  {  
           i++;  
    }  else  {  
           i-­‐-­‐;  
    }  
    if(a || b) {
    
    i++;
    
    } else {
    
    i--;
    
    }
    
    if(a && b) {
    
    i--;
    
    } else {
    
    i--;
    
    }
    
    Mutate  it  
    

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34. Kill  it  
    

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35. mvn  test  
    ant  -­‐f  javalanche.xml  mutaZonTest  
    Kill  it  
    

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36. Run  tests  
    Green  tests  
    Something’s  
    wrong  
    

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37. Run  tests  
    Red  tests  
    Great  job!  
    

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38. Coverage  data  
    Equivalent  mutant  
    if(index  >=  10)  break  
    and  
    if(index  ==  10)  break  
    Selec1ve  muta1on  
    Parallel  execu1on  
    Choose  your  mutants  wisely  
    Using  code  coverage  to  
    reduce  the  tests  to  run  
    Speed-­‐up  
    The  right  tool  
    

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41. Behavior
     
    tes1ng
     
    JUnit
     
    Property  
    tes1ng
      Muta1on  
    tes1ng
     
    with
     
    ScalaCheck
     
    

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42. How  to  test  string  
    concatenaZon  ?  
    assert(  ("ta"  +  "a")  ==  "taa"  )  
    

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43. How  to  test  string  
    concatenaZon  ?  
    assert(  ("ta"  +  "a")  ==  "taa"  )  
    assert(  ("ta"  +  "b")  ==  "tab"  )  
    

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44. How  to  test  string  
    concatenaZon  ?  
    assert(  ("ta"  +  "a")  ==  "taa"  )  
    assert(  ("ta"  +  "b")  ==  "tab"  )  
    …  
    

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45. How  to  test  string  
    concatenaZon  ?  
    assert(  ("ta"  +  "a")  ==  "taa"  )  
    assert(  ("ta"  +  "b")  ==  "tab"  )  
    assert(  ("ta"  +  "z")  ==  "taz"  )  
    …  
    

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46. How  to  test  string  
    concatenaZon  ?  
    assert(  ("ta"  +  "a")  ==  "taa"  )  
    assert(  ("ta"  +  "b")  ==  "tab"  )  
    assert(  ("ta"  +  "z")  ==  "taz"  )  
    …  
    But  boring  
    

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47. ∀n∈N,  ∃!k∈N  
    (n  =  2k  ⋁  n  =  2k+1)  
    Remember  math  class?  
    ∀n,  n  =  42  
    

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48. val  n:  Int  
    val  k:  Int  
     
    (n  ==  2k  ||  n  ==  2k  +  1)  ==  true  
    (n  %  2    ==  0  ||  n  %  2  ==  1)  ==  true  
     
    In  code  
    

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49. val  a:  String  
    val  b:  String  
     
    ((a+b)  endsWith  b)    ==  true  
    ((a+b)  startsWith  a)    ==  true  
     
    (a+b).length  ==  a.length  +  b.length  
    String  
    concatenaZon  
    properZes  
    

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50. List[Int]  =>  isPalindrome(list)  
     
    (list.reverse  ==  list)  ==>  isPalindrome(list)  
     
    (list.reverse  !=  list)  ==>  !isPalindrome(list)  
    Limits  
    

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52. Behavior  tesZng        Every  day  
    MutaZon  tesZng        CriZcal  code  
    Property  tesZng    à    CriZcal  code  
    Share  and  Enjoy  
    

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53. So  Long,  and  
    Thanks  for  All  
    the  Fish  
    Rémy-­‐Christophe  Schermesser  
    @el_picador  
    

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54. Rémy-­‐Christophe  Schermesser  
    @el_picador  
    Behavior  tesZng  
    Rspec  (ruby)  
    Jasmine  (javascript)  
     
    MutaZon  tesZng  
    Javalanche  (java)  
    Mutant  (ruby)  
    Property  tesZng  
    ScalaCheck  (scala)  
    QuickCheck  (haskell)  
    MrProper  (ruby)  
    

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