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TCR (TEST &&
COMMIT || REVERT)
YOUR BEST TESTING FRIEND AGAINST
LEGACY
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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
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WHAT IS LEGACY
CODE?
"a code without tests” -- Michael C.
Feathers
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A LEGACY CODE IS:
1. hard to understand
2. hard to test
3. hard to change
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How do make the changes easy?
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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.
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LIMBO DANCE
LIMBO LOWER NOW
LIMBO LOWER NOW
HOW LOW CAN YOU GO?
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CAN WE USE TDD?
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WHAT IS TCR?
1. a Development Technique (Like TDD)
2. invented by Oddmund Strømme, Lars Barlindhaug
and Ole Johannessen
3. documented by Kent Beck
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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
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
@Test
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public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
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Assert.assertEquals("1", convert(1));
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}
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...
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
@Test
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public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
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Assert.assertEquals("1", convert(1));
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}
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...
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
@Test
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public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
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Assert.assertEquals("1", convert(1));
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}
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...
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Pass!!!
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
@Test
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public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
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Assert.assertEquals("1", convert(1));
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}
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...
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Pass!!!
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TCR BY EXAMPLE(1)
@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
...
public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
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@Test
public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
Assert.assertEquals("1", convert(1));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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public string convert(int toConvertToFizzBuzz) {
return String.valueOf(toConvertToFizzBuzz);
}
@Test
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public void fizzBuzzConvertorLeavesNormalNumbersAlone() {
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Assert.assertEquals("1", convert(1));
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}
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...
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Pass!!!
Commit
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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);
}
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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);
}
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@Test
public void fizzBuzzConvertorMultiplesOfThree() {
Assert.assertEquals("Fizz", convert(3));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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if(toConvertToFizzBuzz%3==0) {
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return "fizz";
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}
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return String.valueOf(toConvertToFizzBuzz);
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}
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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);
}
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@Test
public void fizzBuzzConvertorMultiplesOfThree() {
Assert.assertEquals("Fizz", convert(3));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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if(toConvertToFizzBuzz%3==0) {
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return "fizz";
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}
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return String.valueOf(toConvertToFizzBuzz);
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}
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if(toConvertToFizzBuzz%3==0) {
return "fizz";
}
@Test
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public void fizzBuzzConvertorMultiplesOfThree() {
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Assert.assertEquals("Fizz", convert(3));
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}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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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);
}
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@Test
public void fizzBuzzConvertorMultiplesOfThree() {
Assert.assertEquals("Fizz", convert(3));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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if(toConvertToFizzBuzz%3==0) {
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return "fizz";
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}
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return String.valueOf(toConvertToFizzBuzz);
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}
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if(toConvertToFizzBuzz%3==0) {
return "fizz";
}
@Test
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public void fizzBuzzConvertorMultiplesOfThree() {
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Assert.assertEquals("Fizz", convert(3));
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}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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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);
}
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@Test
public void fizzBuzzConvertorMultiplesOfThree() {
Assert.assertEquals("Fizz", convert(3));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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if(toConvertToFizzBuzz%3==0) {
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return "fizz";
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}
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return String.valueOf(toConvertToFizzBuzz);
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}
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if(toConvertToFizzBuzz%3==0) {
return "fizz";
}
@Test
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public void fizzBuzzConvertorMultiplesOfThree() {
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Assert.assertEquals("Fizz", convert(3));
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}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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Failed!!!
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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);
}
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@Test
public void fizzBuzzConvertorMultiplesOfThree() {
Assert.assertEquals("Fizz", convert(3));
}
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...
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public string convert(int toConvertToFizzBuzz) {
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if(toConvertToFizzBuzz%3==0) {
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return "fizz";
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}
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return String.valueOf(toConvertToFizzBuzz);
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}
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if(toConvertToFizzBuzz%3==0) {
return "fizz";
}
@Test
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public void fizzBuzzConvertorMultiplesOfThree() {
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Assert.assertEquals("Fizz", convert(3));
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}
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...
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public string convert(int toConvertToFizzBuzz) {
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return String.valueOf(toConvertToFizzBuzz);
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}
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Failed!!!
Revert
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TCR
CHARACTERISTICS
no red step
many tiny commits (same message/ no message)
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What About using it in a real used codebase?
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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)
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LIMIT OF CLASSIC
TCR (IN OUR CASE)
1. needed Red Phase
2. almost no production code to produce
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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
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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)
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TAKE AWAY
1. forces you te take small steps
2. less merging problems
3. revert Phase is frustrating (but)
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THANK YOU FOR ATTENDING
Questions ?
twitter: @khaledsouf
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