TCR is your best friend against legacy

I'm sure you tried testing your legacy. It's been complicated sometimes, almost impossible. Kent Beck, the creator of TDD, has come with new testing approach: Test Commit or Revert.
And believe me it's really efficient!

In this talk I'll give my feedback based on a real refactoring legacy project with TCR, the tips, the traps.

Transcript

1. TCR (TEST && COMMIT || REVERT) YOUR BEST TESTING FRIEND AGAINST LEGACY 1
3. ABOUT ME Developer/Crafting Software Coach/Trainer with 13 years Experience working for Zenika Montréal Co-organizer of Software Crafters Montréal meetup Co-organizer of SOCRATES Canada unconference more details on : https://ksouf.com 3
4. WHAT IS LEGACY CODE? "a code without tests” -- Michael C. Feathers 4
6. A LEGACY CODE IS: 1. hard to understand 2. hard to test 3. hard to change 6
7. How do make the changes easy? 7
9. LIMBO: SCALING SOFTWARE COLLABORATION (PRINCIPLES) 1. Everyone is working on (and production is executing) the same program. 2. No one is allowed to cause others (including users) problems. 3. scales technical collaboration by propagating tiny changes instantly. 9
10. LIMBO DANCE LIMBO LOWER NOW LIMBO LOWER NOW HOW LOW CAN YOU GO? 10
12. CAN WE USE TDD? 12
15. WHAT IS TCR? 1. a Development Technique (Like TDD) 2. invented by Oddmund Strømme, Lars Barlindhaug and Ole Johannessen 3. documented by Kent Beck 15
16. HOW TCR WORK? 1. write test (with just enough code to pass) 2. run the test 3. if Pass Commit else Revert 4. Hidden Rule: it's highly recommended to cheat 16
17. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 17
18. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 return String.valueOf(toConvertToFizzBuzz); 7 } 8 17
19. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 return String.valueOf(toConvertToFizzBuzz); 7 } 8 public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } @Test 1 public void fizzBuzzConvertorLeavesNormalNumbersAlone() { 2 Assert.assertEquals("1", convert(1)); 3 } 4 ... 5 6 7 8 17
20. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 return String.valueOf(toConvertToFizzBuzz); 7 } 8 public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } @Test 1 public void fizzBuzzConvertorLeavesNormalNumbersAlone() { 2 Assert.assertEquals("1", convert(1)); 3 } 4 ... 5 6 7 8 17
21. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 return String.valueOf(toConvertToFizzBuzz); 7 } 8 public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } @Test 1 public void fizzBuzzConvertorLeavesNormalNumbersAlone() { 2 Assert.assertEquals("1", convert(1)); 3 } 4 ... 5 6 7 8 Pass!!! 17
22. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 return String.valueOf(toConvertToFizzBuzz); 7 } 8 public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } @Test 1 public void fizzBuzzConvertorLeavesNormalNumbersAlone() { 2 Assert.assertEquals("1", convert(1)); 3 } 4 ... 5 6 7 8 Pass!!! 17
23. TCR BY EXAMPLE(1) @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } ... public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 @Test public void fizzBuzzConvertorLeavesNormalNumbersAlone() { Assert.assertEquals("1", convert(1)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 return String.valueOf(toConvertToFizzBuzz); 7 } 8 public string convert(int toConvertToFizzBuzz) { return String.valueOf(toConvertToFizzBuzz); } @Test 1 public void fizzBuzzConvertorLeavesNormalNumbersAlone() { 2 Assert.assertEquals("1", convert(1)); 3 } 4 ... 5 6 7 8 Pass!!! Commit 17
24. TCR BY EXAMPLE(2) @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } ... public string convert(int toConvertToFizzBuzz) { if(toConvertToFizzBuzz%3==0) { return "fizz"; } return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 9 10 11 18
25. TCR BY EXAMPLE(2) @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } ... public string convert(int toConvertToFizzBuzz) { if(toConvertToFizzBuzz%3==0) { return "fizz"; } return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 9 10 11 @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 if(toConvertToFizzBuzz%3==0) { 7 return "fizz"; 8 } 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 18
26. TCR BY EXAMPLE(2) @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } ... public string convert(int toConvertToFizzBuzz) { if(toConvertToFizzBuzz%3==0) { return "fizz"; } return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 9 10 11 @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 if(toConvertToFizzBuzz%3==0) { 7 return "fizz"; 8 } 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 if(toConvertToFizzBuzz%3==0) { return "fizz"; } @Test 1 public void fizzBuzzConvertorMultiplesOfThree() { 2 Assert.assertEquals("Fizz", convert(3)); 3 } 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 7 8 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 18
27. TCR BY EXAMPLE(2) @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } ... public string convert(int toConvertToFizzBuzz) { if(toConvertToFizzBuzz%3==0) { return "fizz"; } return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 9 10 11 @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 if(toConvertToFizzBuzz%3==0) { 7 return "fizz"; 8 } 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 if(toConvertToFizzBuzz%3==0) { return "fizz"; } @Test 1 public void fizzBuzzConvertorMultiplesOfThree() { 2 Assert.assertEquals("Fizz", convert(3)); 3 } 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 7 8 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 18
28. TCR BY EXAMPLE(2) @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } ... public string convert(int toConvertToFizzBuzz) { if(toConvertToFizzBuzz%3==0) { return "fizz"; } return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 9 10 11 @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 if(toConvertToFizzBuzz%3==0) { 7 return "fizz"; 8 } 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 if(toConvertToFizzBuzz%3==0) { return "fizz"; } @Test 1 public void fizzBuzzConvertorMultiplesOfThree() { 2 Assert.assertEquals("Fizz", convert(3)); 3 } 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 7 8 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 Failed!!! 18
29. TCR BY EXAMPLE(2) @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } ... public string convert(int toConvertToFizzBuzz) { if(toConvertToFizzBuzz%3==0) { return "fizz"; } return String.valueOf(toConvertToFizzBuzz); } 1 2 3 4 5 6 7 8 9 10 11 @Test public void fizzBuzzConvertorMultiplesOfThree() { Assert.assertEquals("Fizz", convert(3)); } 1 2 3 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 if(toConvertToFizzBuzz%3==0) { 7 return "fizz"; 8 } 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 if(toConvertToFizzBuzz%3==0) { return "fizz"; } @Test 1 public void fizzBuzzConvertorMultiplesOfThree() { 2 Assert.assertEquals("Fizz", convert(3)); 3 } 4 ... 5 public string convert(int toConvertToFizzBuzz) { 6 7 8 9 return String.valueOf(toConvertToFizzBuzz); 10 } 11 Failed!!! Revert 18
30. TCR CHARACTERISTICS no red step many tiny commits (same message/ no message) 19
31. What About using it in a real used codebase? 20
32. CONTEXT less than a Month more than 100 of Bug to fix three deployed applications (Javascript/Java) two Developers (I'm one of them) no prior knowledge about the existing code (or applications) 21
34. LIMIT OF CLASSIC TCR (IN OUR CASE) 1. needed Red Phase 2. almost no production code to produce 23
35. RED OR REVERT, GREEN OR REVERT 1. write only the test 2. run the test 3. if Pass Revert else Commit 4. write enough code to Pass 5. if Pass Commit else Revert 24
36. WHAT WE LEARNED 1. we didn't need a build server 2. our code is integrated immediately (Extreme CI) 3. revert Phase is frustrating (but) 25
38. TAKE AWAY 1. forces you te take small steps 2. less merging problems 3. revert Phase is frustrating (but) 27
39. THANK YOU FOR ATTENDING Questions ? twitter: @khaledsouf 28