Matt Parker

@moonmaster9000

TDD(the bad parts)

BUT FIRST

A CAUTIONARY TALE

WHY TDD?

GO FAST FOREVER

GO FAST FOREVER

CLEAN CODE

GO FAST FOREVER

CLEAN CODE

REFACTORING

GO FAST FOREVER

CLEAN CODE

REFACTORING

CONFIDENCE

GO FAST FOREVER

CLEAN CODE

REFACTORING

CONFIDENCE

TESTS

GO FAST FOREVER

CLEAN CODE

REFACTORING

CONFIDENCE

TESTS TDD

PROBLEM #1:

OUTSIDE-IN BDD

1.Write acceptance test

2.Write controller test

3.Write model tests

SLOW

BRITTLE

COUPLED

FLAKY

OUTSIDE?

“Start at the outside

of what you want to

discover” - Joseph

Wilk

OUTSIDE != GUI

PROBLEM #2:

MOCKING

@RequestMapping(value = "/translate", method = REQUEST.POST)

@ResponseBody

public String show(Model model, @RequestParam String word){

return translationService.translate(word);

}

public void post_populatesModel() throws Exception {

TranslationService service = mock(TranslationService.class);

when(service.translate("apple")).thenReturn("appleway");

TranslatorController controller = new TranslatorController(service);

MockMvc mockMvc = standaloneSetup(controller).build();

mockMvc.perform(post("/translate").param("word", "apple"))

.andExpect(model().attribute("translation", "appleway"));}

}

DUMMY

STUB

SPY

MOCK

-----------------------

FAKE

THE LITTLE MOCKERblog.8thlight.com/uncle-bob/2014/05/14/TheLittleMocker.html

S.O.L.I.D.● cleancoders.com

● Agile Software Development:

Principles, Patterns, and Practices

● Pivotal Labs

HEXAGONAL TDDmoonmaster9000.github.io/hexagonal_tdd_in_ruby

PROBLEM #3:

UNIT TESTING

THREE LAWS OF

ROBOTICS TDD

1. You are not allowed to

write any production code

unless it is to make a

failing unit test pass.

2. You are not allowed to

write any more of a unit

test than is sufficient to

fail.

3. You are not allowed to

write any more production

code than is sufficient to

pass the one failing unit

test.

“Every class should be

paired with a well-

designed unit test”

“Every public method

of every class should

be paired with a well-

designed unit test”

class ClassOneTest {

@Test

public void publicMethodOne {

//...

}

@Test

public void publicMethodTwo {

//...

}

ClassOne.java

ClassOneTest.java

ClassTwo.java

ClassTwoTest.java

<REFACTORING>

DESIGN PATTERN!

class ClassOneTest {

@Test

public void publicMethodOne {

//MOVED SOME TESTS

}

//...

class ClassThreeTest {

@Test

public void publicMethodOne {

//TESTS MOVED FROM ClassOneTest

}

//...

ClassOne.java

ClassOneTest.java

ClassTwo.java

ClassTwoTest.java

ClassThree.java

ClassThreeTest.java

TEST COUPLING

DESIGN PATTERNS

GO FAST FOREVER

CLEAN CODE

REFACTORING

CONFIDENCE

TESTS TDD

GO FAST FOREVER

CLEAN CODE

REFACTORING

CONFIDENCE

TESTS TDD

GO FAST FOREVER

CLEAN CODE

REFACTORING

CONFIDENCE

TESTS TDD

“Every class should be

paired with a well-

designed unit test”

“Every class should be

paired with a well-

designed unit test”

“Every behavior should

be paired with a well-

designed unit test”

MINIMIZE SURFACE

AREA

So….

THANK YOU

QUESTIONS?