EMBRACING THE RED BARA TECHNIQUE FOR SAFELY

REFACTORING YOUR TEST CODEM. Scott Ford (@mscottford) | Chief Code Whisperer and CTO | Corgibytes (@corgibytes)

CREDITSLIZ KEOGH ( ) -

MICHAEL FEATHERS ( ) -

@LUNIVORE ORIGINAL ARTICLE

@MFEATHERS ORIGINAL ARTICLE

JARGON ALERTWHAT'S A RED BAR?

GREEN BAR: ALL TESTS PASSING

RED BAR: SOME TESTS FAILING

BEWARE OF OVERCONFIDENCE

A CAUTIONARY TALE

TEST CODE VS PRODUCTION CODE

KEEP YOUR TEST CODE CLEAN

NORMAL TDD CYCLE

ENSURES THAT YOUR TESTS WILL FAIL IF YOUR PRODUCTION CODE BREAKS

ALLOWS YOU TO REFACTOR YOUR PRODUCTION CODE WITH IMPUNITY

RED-BAR CYCLE

RED, REFACTOR, GREENENSURES THAT YOUR TEST CODE CONTINUES TO DETECT THE FAILURE CONDITION WHILE

REFACTORING THE TEST CODE

REDMUTATE THE PRODUCTION CODE

Produces a red barEnsures that your test can fail

REFACTOR

REFACTOR YOUR TESTS

Continue to see the red barEnsures that your tests are still failing

GREENREVERSE THE PRODUCTION CODE MUTATION

Bar should switch to greenYour test should now pass

 

 

 

 

 

THINGS THAT CAN GO WRONG

REDI want to refactor a test, but I can't make it fail

REFACTOR

I'm refactoring a test, and it's started passing

GREENI reverted my production change, and my tests are still failing

CALCULATOR EXAMPLE

STARTING POINT

class Calculator def add(left, right) end end

FAILING TEST

describe 'additon' do specify 'adding two numbers that result in 4' do calculator = Calculator.new result = calculator.add(2, 2) expect(result).to eq(4) end end

WATCH IT FAIL

WATCH IT FAIL

MAKING IT PASS

class Calculator def add(left, right) return 4 end end

WATCH IT PASS

WATCH IT PASS

MAKE THE TESTS BETTER

describe 'additon' do specify 'adding two numbers that result in 4' do calculator = Calculator.new result = calculator.add(2, 2) expect(result).to eq(4) end

specify 'adding two numbers that result in 5' do calculator = Calculator.new result = calculator.add(2, 3) expect(result).to eq(5) end end

WATCH THEM FAIL

WATCH THEM FAIL

MAKE THEM PASS

class Calculator def add(left, right) return left + right end end

WATCH THEM PASS

WATCH THEM PASS

LET'S REFACTOR OUR TESTS

BREAK THE PRODUCTION CODEclass Calculator def add(left, right) return 0 # was: left + right end end

WATCH THE TESTS FAIL

WATCH THE TESTS FAIL

APPLY THE REFACTORINGdescribe 'additon' do let(:calculator) { Calculator.new }

specify 'adding two numbers that result in 4' do result = calculator.add(2, 2) expect(result).to eq(4) end

specify 'adding two numbers that result in 5' do result = calculator.add(2, 3) expect(result).to eq(5) end end

VERIFY THAT THE TESTS STILL FAIL

VERIFY THAT THE TESTS STILL FAIL

RESTORE PRODUCTION CODEclass Calculator def add(left, right) return left + right end end

WATCH THE TESTS PASS

WATCH THE TESTS PASS

 

 

 

 

 

QUESTIONS?

CONTACT INFO

M. Scott FordTwitter: @mscottfordBlog: http://corgibytes.com/blog