Luca@gerritforge.comhttp://www.gerritforge.comTwitter: @gitenterprise

TDDDead or Alive?

Luca Milanesio

GerritForge

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About me

Luca MilanesioCo-founder of GerritForge

over 20 years of experience in Agile Development SCM and ALM worldwide

Contributor to Jenkins since 2007 (and previously Hudson)

Git SCM mentor for the Enterprise since 2009

Contributor to Gerrit Code Review community since 2011

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Agenda Why? TDD-induced damage Evangelist vs. Professional Reboot Professional TDD Learning to write

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TDD is 20 years old

http://www.macqueen.us/smalltalkReport/ST/91_95/SMAL0402.PDF

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TDD has been widely adopted

http://www.indeed.com/jobtrends?q=test+driven+development&relative=1

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Hold on … what's that ?

http://www.indeed.com/jobtrends?q=test+driven+development&relative=1

?

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… and that ?

http://martinfowler.com/articles/is-tdd-dead/

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Test-induced design damageBy David Heinemeier Hansson on April 29, 2014

http://david.heinemeierhansson.com/2014/test-induced-design-damage.html

"Code that's hard to test in isolation is poorly designed", goes a common TDD maxim. Isolation meaning free of dependent context and separated from collaborators, especially "slow" ones like database or file IO. The prevalent definition of "unit" in unit testing (though not everyone agrees with this).

This is some times true. Some times finding it difficult to test points to a design smell. It may be tangled responsibilities or whatever. But that's a far ways off from declaring that hard-to-unit-test code is always poorly designed, and always in need of repair. That you cannot have well-designed code that is hard to unit test.

It's from this unfortunate maxim that much of the test-induced design damage flows. Such damage is defined as changes to your code that either facilitates a)

easier test-first, b) speedy tests, or c) unit tests, but does so by harming the clarity of the code through — usually through needless indirection and conceptual overhead. Code that is warped out of shape solely to accommodate testing objectives.

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TDD EXAMPLE DAMAGE ON A

LARGE PROJECT

https://www.flickr.com/photos/martinluff/5475631631

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Code metrics of one service

340 Java Classes880 Tests158 Mocks

99.5% Code Coverage

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TDD seniority and practices

Devs with two digits' years' experienceTDD applied with discipline from start

Code constantly covered by testsBuild time: 2 minutes (~ 130 msec per

test)

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Test example

@Test public void shouldGetNewDTOFromEntity() { // Given DTO expectedDTO = DTOFixture.getDefaultRewardWithOneVariant().build(); Reward entity = VariantRewardFixture.getDefaultRewardWithOneVariant().build();

// When DTO variantDTO = entity.transformToDTO();

// Then assertThat(variantDTO, is(not(nullValue()))); assertThat(variantDTO, is(reflectionEquals(expectedDTO))); }

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Code example

public DTO transformToDTO() { String id = getId() == null ? null : getId().toString();

DTO dto = DTO.forVariants(); dto.setId(id); dto.setName(getName()); dto.setDescription(getDescription()); dto.setShortDescription(getShortDescription()); dto.setStatus(getStatus()); dto.setRewardItemType(getRewardItemType()); dto.setDeliveryMechanism(getDeliveryMechanism()); dto.setTermsAndConditions(getTermsAndConditions()); dto.setStockLimited(isStockLimited()); dto.setImages(transformImagesToDTOs(getImages()));

for (Variant variant : getVariants()) { dto.addVariant(variant.transformToDTO()); }

return dto; }

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THAT'S GOOD TDDOR NOT?

http://icongal.com/gallery/icon/17045/256/thumbs_up_thumbs_up_vote_like

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Features velocity

For every new feature we did:End-to-End user-journeys acceptance testService-to-Service integration testComponent-to-component integration testsUnit tests (with mocks)

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… and their planning meeting

[TechLead] "How many points for this story ?"[Devs] "2 .. 5 .. 5 .. 5"[TechLead] "5 ? C'mon … for that small change?"[Devs] "Change is trivial, but it will take some time

to amend all the tests and getting a green build"

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But with more quality?

At the beginning yes Project grew, tests base grew as well Breaking tests became the norm Less frequent refactor, for not breaking

tests Tech debt increased over time

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WHAT WENT WRONG?

https://www.flickr.com/photos/crystalflickr/145082274

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I AM NOT TDD EVANGELIST

Evangelists are "relaying information about a particular set of beliefs with the intention of converting the recipient"

http://en.wikipedia.org/wiki/Technology_evangelist

http://school.point2educate.com/wp-content/uploads/2014/03/Book-Red.png

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I AMTDD

PROFESSIONALProfessionals are "members of the profession with the particular

knowledge and skills necessary to perform the role of that profession"http://en.wikipedia.org/wiki/Professional

http://www.levantar.co.uk/images/images/Lean_Legal_Professional_Firms.jpg

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PROFESSIONAL TDD

REBOOT

http://png-2.findicons.com/files/icons/75/i_like_buttons_3a/512/perspective_button_standby.png

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Step 1 – TEST RED

Write the test, without any code written yetRED: test fails

(compilation errors are considered failures as well)

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Step 2 – TEST GREEN

Make test work as quickly as possibleGREEN: test passes

(code satisfies the test assertions)

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Step 3 – CODE REFACTOR

Keep the test code unchangedRework the implementation to make it

clean, DRY, flexibleGREEN: new code passes the test

(reworked code behaves exactly as before)

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TESTIS THE HEAD

OF ALL TDD CYCLE

http://www.improveit.mx/Imagenes/tdd_esquema_en.jpg

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TDD ASSUMES

THAT TEST IS

CORRECT

http://www.wisteriaformations.co.uk/articles/wp-content/uploads/2011/09/Company-Formation-15.jpg

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BUT WHAT IF TEST

IS NOT 100% CORRECT?

http://blogs.warwick.ac.uk/images/fsavva/2012/04/16/question-mark-man.jpg?maxWidth=500

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ANOTHER POSSIBLE DIFFERENT REALITY

http://www.gamerzines.com/wp-content/uploads/2014/03/morpheus-chair.jpg

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Step 1 – TEST RED-ish

Write the [incorrect] test, no code exists yetRED: fails, but maybe the test is wrong?

(nothing works, who can tell what is really wrong?)

?

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Step 2 – TEST GREEN-ish

Make test work as quickly as possibleGREEN: [incorrect] test passes

(is code correct or wrong? nobody really knows)

?

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Step 3 – CODE REFACTOR-ish

Keep the test code unchangedRework the implementation to make it

clean, DRY, flexibleGREEN: reworked code passes the tests

(was the code correct before? Is the code still correct after?)

?

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?

What is TESTING?

How to TEST the length of a table?

Use your foot Or a RULER?

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How can I test the TEST?

How do you test a ruler?

?

Your thumb?

Or a digital caliper?

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And how can I test the test of a TEST?

How do you test a digital caliper?YOU DON'T

[One meter is express in terms of speed of light]

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Test and accuracy

TEST has to be MORE ACCURATE

than CODE

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Test and confidence

TEST cannot be testedbut we have

CONFIDENCE to beVALID

K = 299,792,458 m / s

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Can this test @Test public void shouldRedisplayEditFormWhenErrorAndUserKeyExists() {

boolean partnerTokenExists = true; setupForRedisplayEditFormWhenError(partnerTokenExists);

ModelAndView mav = partnerController.update(RESOURCE_URI, mockUserPayload, mockBindingResult, mockSessionStatus); verify(mockUserPayload, times(2)).getUserSupplyTypesCodes(); assertThat(mav.getViewName(), equalTo("administration/partners/edit")); assertThat(mockUserPayload.getUserSupplyTypesCodes().size(), equalTo(1)); assertThat(mockUserPayload.getUserSupplyTypesCodes().iterator().next(), equalTo("Identity"));

verify(mockSessionStatus, never()).setComplete(); verify(mockCountryService, times(1)).getAllCountries(); verify(mockUserService, times(1)).getAllSupplyTypes();

} private void setupForRedisplayEditFormWhenError(boolean partnerTokenExists) { when(mockBindingResult.hasErrors()).thenReturn(true); when(mockUserPayload.getTokensDefined()).thenReturn(partnerTokenExists); when(mockUserPayload.getUserSupplyTypesCodes()).thenReturn(new HashSet<String>()); when(batchService.getAllByUser(anyString())).thenReturn(null); UserRole partnerRole = new UserRole("PTN1"); partnerRole.setIssuingUser(true); when(mockCurrencyManager.getUserRoles(any(String.class))).thenReturn(new UserRole());

Errors errors = new Errors(); when(mockValidationErrorsException.getViolations(any(ViolationSeverity.class))).thenReturn(errors); doThrow(mockValidationErrorsException).when(mockUserService).updateUser(any(UserPayload.class), any(URI.class));

}

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Be more accurate than this code ?

@RequestMapping(value = "/edit", method = RequestMethod.POST) public ModelAndView update(@RequestParam String resourceId, @ModelAttribute(PARTNER) UserPayload partner, BindingResult result, SessionStatus status) { boolean isTokenExists = partner.getTokensDefined(); if (partner.getUserSupplyTypesCodes() == null) partner.setUserSupplyTypesCodes(new HashSet<String>()); if (isTokenExists) partner.getUserSupplyTypesCodes().add("Identity");

UserRole partnerRole = currencyManager.getUserRoles(partner.getCode());

if (partnerRole.isIssuingUser()) partner.getUserSupplyTypesCodes().add("Issuance"); if (partnerRole.isLiabilityUser()) partner.getUserSupplyTypesCodes().add("Liability");

try { partnerService.updateUser(partner, URI.create(resourceId)); status.setComplete(); return new ModelAndView("redirect:/partners"); } catch (ValidationErrorsException e) { SpringErrorBindingHelper.populateErrors(result, e.getViolations(ViolationSeverity.ERROR)); ModelAndView mav = new ModelAndView("administration/partners/edit"); partnerRole = currencyManager.getUserRoles(partner.getCode()); mav.addObject(PARTNER_ROLE, partnerRole); mav.addObject(RESOURCE_ID, resourceId); populateReferenceData(mav); return mav; } }

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And this test?

"Sending two JSON records to the messages REST API" should {

"returns HTTP Status 200 and store two records to the messages repository" in {

// Given val jsonRows = Json.parse( """[ |{ "id": "1234567890", "form": "SA300", "dispatchOn": "2013-11-22", "detailsId": "W0123456781234569"}, |{ "id": "1234567891", "form": "SA316A", "dispatchOn": "2013-11-23", "detailsId": "C0123456781234568"} |]""".stripMargin)

// When verifyStatusCode(doPut(resource(s"/messages"), jsonRows), 200)

// Then val messages = await(messageRepository.findAll) messages should have size 2

exactly(1, messages) should have ( 'recipient("1234567890"), 'body("SA300", DetailsId("W0123456781234569")), 'dispatchOn(new LocalDate(2013, 11, 22)) )

exactly(1, messages) should have ( 'recipient("1234567891"), 'body("SA316A", DetailsId("C0123456781234568")), 'validFrom(new LocalDate(2013, 11, 23)) ) }}

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Compared to this code ?

def putMessages = Action.async(action.parser) { implicit request => withJsonBody[List[PrintSuppressionNotification]] { messages => if (messages == null || messages.isEmpty) throw new BadRequestException("No messages supplied") if (messages.size > maxMessages) throw new RequestEntityTooLargeException( s"${messages.size} items submitted, max $maxMessages allowed") val results = mongo.insertAllUnique(messages.map(_.toMongo)) Future.sequence(results).map(_ => Results.Ok) } }

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Other projects' testimonials

"Today however, my team told me the tests are more complex than the actual code. (This team is not the original team that wrote the code and unit tests. Therefore some unit tests take them by surprise. This current team is more senior and

disciplined.) In my opinion, now that’s waste..."

Richard Jacobs at Sogeti (Sogeti Nederland B.V.) http://www.rbcs-us.com/documents/Why-Most-Unit-Testing-is-

Waste.pdf

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Accurate = Small

More code =

more mistakes

Ideal size of a test? ~ 3 lines Assumption, Action, Assertion

"Less is more"[Ludwig Mies van der

Rohe]

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Accurate = Readable

We can trust what we understandMake your test easy to read

Anyone would understand and validate it

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Accurate = Explicit and repeatable

What You See is What Test DoesAgain and again the same

No side-effects No hidden logic in helper

No loopsNo random values

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Accurate = Traceable to a requirement

When test fails,what stops working?

Use business domain namesuse business stories names

for objects, actions and results

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Accurate = Correct when fails

If I comment out a line of code, does the test FAIL for the CORRECT reason?Does the test returns an error (exception)

instead of a failure?

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WHOOPS!MY TESTS ARE INACCURATE,

WHAT SHOULD I DO?

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INACCURATE TESTIS WORSE THAN

NO TEST

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Are you telling me I should have less tests ?Q [John Nolan]:

"The thing I've found about TDD is that its takes time to get your tests set up and being naturally lazy I always want to write as little code as possible. The first thing I seem do is test my constructor has set all the properties but is this overkill?My question is to what level of granularity do you write you unit tests at?

..and is there a case of testing too much?"

A [Kent Beck]:

"I get paid for code that works, not for tests, so my philosophy is to test as little as possible to reach a given level of confidence"

http://stackoverflow.com/questions/153234/how-deep-are-your-unit-tests/153565#153565

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REBUILDINGPROFESSIONAL TDD

https://www.flickr.com/photos/jdn/4817970175

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Experience over Rules

Writing CODE is MORE than applying RULES

Reading CODE is MORE than reading BOOKS

Common sense, Trial and Error

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The Sense of Time

Test too complex to write ? Kill the test (if the code is clean)

Test takes too long to understand? Kill the test (if the code is readable)

Time (with TDD) < Time (without TDD)or you are doing something wrong!

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Cost / value trade-off

Writing tests costs moneyTest marginal value > Test cost?

Is this code critical? Can it possibly fail? Am I double-testing something

covered?

Cost (with TDD) < Cost (without TDD)or you are doing something wrong!

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How big is my code-base with TDD?How many test / code lines I am

writing?Confidence on uncovered code?

Size (Test) < Size (Code)Do not test code that cannot break

Test / code ratio

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Test Focus

Tests express WHAT to achievefrom user's perspective

Test WHAT can be measured

What can I measure on this?public interface UserRepository { void addUser(String username, String first, String last);}

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Code confidence

Code (not Test) tells HOW system works

Code (with Test) gives confidence of correctness

We are confident on what is clear + readable + repeatable

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Writing code - Martin Fowler

"Any fool can write code that a computer can understand. Good programmers write code that humans can understand.”

[Martin Fowler - 1999 - Refactoring: Improving the Design of Existing Code]

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Best writers in history – Ernest Hemingway"In 1954, when Hemingway was awarded the Nobel Prize for Literature, it was for his mastery of the art of narrative […] He avoided complicated syntax. About 70 percent of the sentences are simple sentences—a childlike syntax without subordination."

http://en.wikipedia.org/wiki/Ernest_Hemingway

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Reading = learning to Write

Code ReviewRead A LOT of code

Read good code, read bad code

Comment, exchange ideasChallenge solutions

https://www.flickr.com/photos/jdn/4817970175

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Write, experiment, throw waste

Write code, ask for feedbackRead your own code …

after days, weeks, monthsMeasure progress

Throw wasteKeep test and code clean, ALWAYS

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Professional TDD Summary

1. TDD practices are not enough2. Experience over Rules3. Trade-off test time/cost and code benefit4. Tests is WHAT to achieve5. Code is confidence on DESIGN6. Read code to become a better writer7. Plan to throw test waste away

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TDD resources for reading and learning Is TDD dead hangouts series

http://martinfowler.com/articles/is-tdd-dead/

Unit-testing and waste managementhttp://www.rbcs-us.com/documents/Why-Most-Unit-Testing-is-Waste.pdf

Mockist vs. non-mockist TDDhttp://martinfowler.com/articles/mocksArentStubs.html

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Code-review resources

Guido Van Rossum about Code Review @Googlehttp://www.youtube.com/watch?v=CKjRt48rZGk

Code Review @SAPhttp://www.eclipsecon.org/2013/sites/eclipsecon.org.2013/files/CodeReview.pptx

V. Subramaniam – About Code Review and Qualityhttp://www.agiledeveloper.com/presentations/caring_about_code_quality.pdf

Replay these slides:http://slideshare.net/lucamilanesio

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