TDD CrashCourse Part2: TDD

02 BARCELONA
David Ródenas, PhD
TDD Course
TEST DRIVEN
DEVELOPMENT

@drpicox
Breaking myths and understanding why
Software Values

The Triangle △ Example

Fixing Code Smells

Discipline

The Rules

TDD is Dead

TDD vs. BDD

Tips for adoption
TEST DRIVEN DEVELOPMENT

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QUIZ
4
TDD — SOFTWARE VALUE
WHICH IS THE MAIN
SOFTWARE VALUE?

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PRIMARY VALUE

The ability to tolerate and facilitate change
SOFTWARE VALUES
5
TDD — SOFTWARE VALUES
SECONDARY VALUE

The current software meets the current needs of the current user

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ARE YOU A FORTUNE TELLER?
6
There are no oracles.

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Rigidity

Dif
f
icult to change

Fragility

Changes breaks unrelated features

Immobility

Cannot extract/reuse a module

Needless complexity

Too much anticipation
CODE SMELLS
7

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FIXING CODE SMELLS
TDD 8

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WATERFALL DESIGN
9
TDD — FIXING CODE SMELLS
Code
The

Great

Refactor
Upfront

Design
Code Code Code Code
time
speed

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10

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DESIGN YOUR WAY
11
Refactor
Code Code Code Code
Refactor
Code
Refactor
Code Code Code
Refactor
time
speed
THE AGILE

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How we know that we break no feature?
BUT REFACTOR IS DANGEROUS
12

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LEVERAGE ON TESTS
13
CODE
TESTS
*we assume that we have good tests

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Tests do also suffer from code smells

If a test is fragile, we cannot leverage on them to refactor code
BUT...
14
Refactor
TESTS
?

@drpicox
—Merriam-Webster dictionary
"DISCIPLINE:

TRAINING THAT CORRECTS, MOLDS, OR
PERFECTS THE MENTAL FACULTIES OR
MORAL CHARACTER"
TDD — DISCIPLINE 16

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@drpicox
Accounting is a discipline that is in charge of
studying, measuring and analyzing the assets
and
f
inancial and economic situation of a
company or organization, in order to facilitate
decision-making within it and external control,
presenting the information , previously
registered, in a systematic and useful way for
the different interested parties.
 
ACCOUNTING
17
TDD — DISCIPLINE
—Wikipedia
Double-entry bookkeeping
In 70 AD Plinius the Elder described

the structure of the "Tabulae Rationum".
Account Debit Credit
Furniture $1,500
Cash $1,500
$1,500 $1,500

@drpicox
@drpicox
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 suf
f
icient to fail; and compilation
failures are failures.

3. You are not allowed to write any more
production code than is suf
f
icient to pass the
one failing unit test.
PROGRAMMING
18
TDD — DISCIPLINE

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UNDERSTANDING DA RULES
TDD 19

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It is a discipline of programming

about coding

about testing

and about design
 
(in the form of refactoring)
WHAT IS TDD?
20
TDD — THE RULES

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The steps are the following:

write a “single” test describing an aspect of the program

run the test, which should fail because the program lacks that feature

write “just enough” code, the simplest possible, to make the test pass

“refactor” the code until it conforms to the simplicity criteria

repeat, “accumulating” unit tests over time
HOW FOLLOW THE RULES?
21
TDD — THE RULES
Write a Test
✘ Test Fails
✔ Test Passes
Write the Code
✔ Test Passes
Clean Code and Tests

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WHO TESTS THE TEST?
22
TDD — THE RULES
Write a Test
✘ Test Fails
✔ Test Passes
Write the Code
✔ Test Passes
We know that code

works because tests.
We know that clean broke

nothing because tests.
It the test failing

who tests the test.
TDD SILVER RULE

You shall make tests fail
f
irst

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?
CODE
HOW TO REFACTOR TESTS?
23
TDD — THE RULES
TESTS

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TDD ESSENTIAL RULES
24
TDD — THE RULES
TDD SILVER RULE

f
irst
TDD GOLDEN RULE

You shall iterate fast

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TDD ESSENTIAL RULES
25
TDD — THE RULES
TDD GOLDEN RULE

Write a Test
✘ Test Fails
✔ Test Passes
Write the Code
✔ Test Passes
30s

loop

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DESIGN YOUR WAY
26
Refactor
Code
time
speed
Refactor
Code
Refactor
Code
Refactor
Code
Refactor
Code
Refactor
Code
Refactor
Code
Refactor
Code
THE TDD

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TDD IS DEAD
TDD — IS DEAD 27

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https://www.infoq.com/news/2014/06/tdd-dead-controversy/
KILLING TDD
28
TDD — IS DEAD
David Heinemeier Hansson, Ruby on Rails author and founder of Basecamp gave
the opening keynote at Railsconf 2014 in which he challenged the value of TDD as
it is often implemented.

«Then I'd try test-first for a few weeks, only to drop it again when it started
 
hurting my designs.»

«"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 […] The
prevalent definition of "unit" in unit testing (though not everyone agrees with this).»

«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 […]. Code that is warped out of shape solely to accomodate testing objectives.»

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https://wiki.c2.com/?DeveloperTest
THE REAL TDD
29
TDD — IS DEAD
Ward Cunningham, inventor of Wiki, writer of the Agile Manifesto, inventor of the
test runner and run docs as test, co-inventor of XP and TDD, inventor of the
technical debt concept.

«A DeveloperTest is the correct name for what the industry generally calls a UnitTest. It
is a test written for developers, as distinct from an AcceptanceTest or CustomerTest,
written for the OnsiteCustomers.»

«Under the strict definition, for QA purposes, the failure of a UnitTest implicates only
one unit. You know exactly where to search to find the bug.»

«TestDrivenDevelopment produces DeveloperTests. The failure of a test case implicates
only the developer’s most recent edit.»

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BOTH AXIS
30
TDD — IS DEAD
+legible
-legible
legibility
DEVELOPER TEST ACCEPTANCE TEST
UNIT TEST
E2E TEST
con
f
idence
-con
f
idence
+con
f
idence
INTEGRATED TEST
Best compromise
Double Con
f
idence

It does what code says

Everyone on same page
Developers fail

with TDD because of

they use the wrong

level of abstraction

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THE ELEPHANT IN THE ROOM
31
TDD — IS DEAD
XY-1516

The new valuable
feature
5
IT2
IT1 IT3 IT4
XY-
 
1516
XY-
 
1517
XY-
 
1518
AA-
 
1121
AA-
 
0987
AA-
 
1122
Last day of IT3
EV-1516 is not

yet
f
inished,

why is that?
Well, the PR is
stopped, it requires

cleaning
Today
ends the iteration,
and there are
dependencies
Approve
that and do

the cleaning
later.
Ok.
Keep technical excellence at all
times

Technical debt charges interest every
feature

No one wants a big refactor

SAFe is Agile

Story points are estimates, not time boxes

Never ever and ever ask for
termination

Ask for new estimates instead, and replan
Continuous attention to
technical excellence

and good design enhances
agility.
https://agilemanifesto.org
* Never congratulate a team for

ff
erent primary value
«I had a problem. While using and teaching agile practices like test-driven development
(TDD) [...], I kept coming across the same confusion and misunderstandings.
Programmers wanted to know where to start, what to test and what not to test, how
much to test in one go, what to call their tests, and how to understand why a test fails.»

«I remember thinking “If only someone had told me that!” far more often than I
thought “Wow, a door has opened.” I decided it must be possible to present TDD in a
way that gets straight to the good stuff and avoids all the pitfalls.»

«At this point, I had a framework that helped me understand – and more importantly,
explain – how TDD works and an approach that avoided all the pitfalls I had
encountered.»

If we could develop a consistent vocabulary for analysts, testers, developers, and the
business, then we would be well on the way to eliminating some of the ambiguity and
miscommunication that occur when technical people talk to business people.

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TDD SILVER RULE

f
irst
TDD GOLDEN RULE

BDD

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TDD SILVER RULE

f
irst
BDD GOLDEN RULE

You shall have a common language
TDD
35
TDD — VS. TDD
TDD SILVER RULE

f
irst
TDD GOLDEN RULE

BDD

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THE PATH
36
TDD — VS. BDD
Acceptance

Test
TDD
BDD
Developer

Test
Feature: Is it Friday yet?

Everybody wants to know when it's Friday

Scenario: Sunday isn't Friday

Given today is Sunday

When I ask whether it's Friday yet

Then I should be told "Nope"
import { isItFridayYet } from '../'

test('Sunday isn't Friday', () => {

const today = new Date('Sunday 8/16/2020');

const answer = isItFridayYet(today);

expect(answer).toBe(false);

});
PO QA Dev
Dev

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BOTH AXIS
37
TDD — VS. BDD
+legible
-legible
legibility
DEVELOPER TEST ACCEPTANCE TEST
UNIT TEST
E2E TEST
con
f
idence
-con
f
idence
+con
f
idence
INTEGRATED TEST
Fast enough for TDD

Create suits and focus
Usually too slow for TDD
TDD
BDD

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TIPS FOR ADOPTION
TDD 38

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Focus the most important suit and run every
minute

Run all developer tests at least every two
hours
RUN TESTS FREQUENTLY
39
TDD — TIPS FOR ADOPTION

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The code is who teaches to the new
members

Testing code should be cleaner than
production code
CODE IS YOUR FRIEND
40

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Once a developer needs to run the
application to develop, TDD is over.
MANUAL TESTING IS YOUR ENEMY
41

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Think in Business Value.

BDD helps to TDD and vice-versa.
MOSTLY INTEGRATED
42
Unit
Test

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MOSTLY INTEGRATED
43

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MOSTLY INTEGRATED
44
The car lights the street

TDD CrashCourse Part2: TDD

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