TDD and the Art of the Minimal Tests "Imagine you are in a room - PowerPoint PPT Presentation

TDD and the Art of the Minimal Tests

"Imagine you are in a room �lled with..."

Serious?

Nah, just casual?

Interested?

Getting introduced?

The beginning of thought is in disagreement - not only with others but also with ourselves. - Eric Ho�er

What is a test?

test /t ɛ st/ "an event or situation that reveals the strength or quality of someone or something by putting them under strain"

What is driven?

driven / ˈ dr ɪ vn/ motivated or determined by a speci�ed factor or feeling

What is development?

Lynoure Braakman

Software engineer

https://www.neuland-b�.de

twitter: @Lynoure #ETC2018

https://lynoure.net

lean & agile

eXtreme Programming (XP)

Test Driven Development

It's not

writing �rst all the tests

(adapted with a permission from turnoff.us)

"Start a painting with fresh ideas, and then let the painting replace your ideas with its ideas." - Darby Bannard

Test Driven Thinking

Red

smallest

test: class TaxIdValidation (TestCase): def test_valid_tax_id (self): tax_id = '24750815087' self.assertTrue(validate_tax_id(tax_id), msg='Test tax id should validate'

smaller

test: class TaxIdValidation (TestCase): def test_valid_tax_id (self): validate_tax_id()

"FAILED (errors=1)"

❤ FAIL

"NameError: name 'validate_iban' is not de�ned"

❤ FAIL

Refreshing failures roll o� the travel easel like ants from a picnic blanket. -Sara Genn

"OK"

That is NOT OK

Green

small

smaller

code: def validate_tax_id (): pass

"OK"

test: class TaxIdValidation (TestCase): def test_valid_tax_id (self): tax_id = '24750815087' self.assertTrue(validate_tax_id(tax_id), msg='Test tax id should validate'

test: class TaxIdValidation (TestCase): def test_valid_tax_id (self): tax_id = '24750815087' self.assertTrue(validate_tax_id(tax_id), msg='Test tax id should validate' code: def test_valid_tax_id (tax_id): if tax_id is '24750815087': return True

YAGNI

YAGNI You Ain't Gonna Need It

"As a software developer, you are your own worst enemy. The sooner you realize that, the better o� you’ll be.” -Je� Atwood

"Many are stubborn in pursuit of the path they have chosen, few in pursuit of the goal." -Friedrich Nietzsche

test: class TaxIdValidation (TestCase): def test_invalid_tax_id (self): tax_id = 'my tax id' self.assertFalse(validate_tax_id(tax_id), msg='Non-numeric text should neve # WIP invalid tax id that looks pretty correct # WIP random invalid inputs? def test_valid_tax_id (self): tax_id = '24750815087' self.assertTrue(validate_tax_id(tax_id), msg='Test tax id should validate'

test: class TaxIdValidation (TestCase): def test_invalid_tax_id (self): tax_id = 'my tax id' self.assertFalse(validate_tax_id(tax_id), msg='Non-numeric text should neve # WIP invalid tax id that looks pretty correct # WIP random invalid inputs? def test_valid_tax_id (self): tax_id = '24750815087' self.assertTrue(validate_tax_id(tax_id), msg='Test tax id should validate' code: def test_valid_tax_id (tax_id): if tax_id is '24750815087': #YAGNI? return True else : return False

❤ FAIL

❤ FAIL ❤ OK

photo CC BY 2.0 Alper Çu ğ un

Refactor

Refactor your code

Refactoring or implementing?

Pause to think

One co�ee with a failing test, please!

Trust your discomfort

More data

test: class TaxIdValidation (TestCase): ... def test_valid_tax_id (self): self.assertTrue(validate_tax_id('24750815087'), msg='Original test tax id

test: class TaxIdValidation (TestCase): ... def test_valid_tax_id (self): self.assertTrue(validate_tax_id('24750815087'), msg='Original test tax id code: def _tax_id_checksum (value): product = 10 for digit in value: total = (int(digit) + product) % 10 product = (total * 2) % 11 checksum = 11 - product if checksum is 10: checksum = 0 return checksum def validate_tax_id (value): value = (value.replace(' ', '')).strip() if not re.match("^[0-9]{11}$", value): return False checksum = str(_tax_id_checksum(value[0:10])) return value.endswith(checksum)

Almost done!

test: class TaxIdValidation (TestCase): ... def test_valid_tax_id (self): self.assertTrue(validate_tax_id('24750815087'), msg='Original test tax id self.assertTrue(validate_tax_id('12345678903'), msg='Second test tax id sho

test: class TaxIdValidation (TestCase): ... def test_valid_tax_id (self): self.assertTrue(validate_tax_id('24750815087'), msg='Original test tax id self.assertTrue(validate_tax_id('12345678903'), msg='Second test tax id sho code: def _tax_id_checksum (value): product = 10 for digit in value: total = (int(digit) + product) % 10 product = (total * 2) % 11 checksum = 11 - product if checksum is 10: checksum = 0 return checksum def validate_tax_id (value): value = (value.replace(' ', '')).strip() if not re.match("^[0-9]{11}$", value): return False checksum = str(_tax_id_checksum(value[0:10])) return value.endswith(checksum)

"FAILED (failures=1)"

code: def _tax_id_checksum (value): product = 10 for digit in value: total = (int(digit) + product) % 10 if total is 0: # This was missing total = 10 product = (total * 2) % 11 checksum = 11 - product if checksum is 10: checksum = 0 return checksum def validate_tax_id (value): value = (value.replace(' ', '')).strip() if not re.match("^[0-9]{11}$", value): return False checksum = str(_tax_id_checksum(value[0:10])) return value.endswith(checksum)

The plural of 'test input' is not 'test data'

"What would you recommend I use for test data?"

Giving back to the testers

Refactor the tests as well

What kind of tests?

Test pyramids

(CC BY 2.0 Jerome Bon)

(CC BY 2.0 Sheila Sund)

(CC BY-SA 2.0 John Morton)

(by Staffan Andersson)

Good tests alert you to take action, and make it easy to �gure out what kind of action to take

TDD alone and with others

Alone

Whole team does TDD

No one does TDD

First in the team doing TDD

First in the team doing TDD

First in the team doing TDD

A pair of programmers is happier than one

If you CI something, it says something

Simple recipe for more and better TDD: 1. Come up with a tiny test for it

Simple recipe for more and better TDD: 1. Come up with a tiny test for it 2. Take the smallest action that can take you there

Simple recipe for more and better TDD: 1. Come up with a tiny test for it 2. Take the smallest action that can take you there 3. Once you got there, re�ect and adjust

Simple recipe for more and better TDD: 1. Come up with a tiny test for it 2. Take the smallest action that can take you there 3. Once you got there, re�ect and adjust 4. Repeat

The End 2018 CC BY-SA 2.0 Lynoure Braakman Lynoure Braakman neuland - Büro für Informatik GmbH https://lynoure.net https://www.neuland-bfi.de @Lynoure #ETC2018