Introduzione al TDD

Introduzione al
Test Driven Development
Andrea Francia
http://www.andreafrancia.it

Contents
Concepts
Definition
Example1: Parser
Example2: Text To Speech

Concepts
Test First
Automate tests

Automated Test Lifecycle
Giordano Scalzo: http://www.slideshare.net/giordano/tdd-iphonefordummies

Automated Test Lifecycle
SUT: System Under Test

Example of a Manual Test:
nextLine()
public static void main(String[] args) {
String text = "first linensecond line";
Scanner scanner = new Scanner(text);
System.out.println(scanner.nextLine()); // prints
"first line"
System.out.println(scanner.nextLine()); // prints
"second line”
}
Code:

assertEquals(expected, actual);
PASS FAIL
expected == actual
yes no

Using JUnit
@Test public void howNextLineWorks() throws IOException {
String text = "first linensecond line";
Scanner scanner = new Scanner(text);
assertEquals(”first line", scanner.nextLine());
assertEquals(”second line", scanner.nextLine());
}
Code:
Output:

What is Test Driven
Development?

What is TDD?
Test-driven development (TDD) is a software
development process that relies on the repetition of a
very short development cycle:
Tim Ottinger:http://agileinaflash.blogspot.com/2009/02/red-green-refactor.html

RED
first the developer writes a failing automated test case
that defines a desired new behaviour (of the software),

GREEN
then produces code to pass that test …

Refactor
and finally refactors the new code to acceptable standards.

Example:
Writing “df” Parser

The df output
[andreafrancia@deneb Dropbox]$ df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/disk0s2 243862672 135971832 107634840 56% /
/dev/disk0s1 243862672 135971832 107634840 56% /tmp
/dev/disk1s2 243862672 135971832 107634840 56% /opt
devfs 109 109 0 100% /dev
Mount Points

The problem
List all mount points

The Problem
Write a method that extract the list of the mount points
from the output of df.

First of all decompose
the problem!

Decomposition
Parse the output of “df” process …
When there are no mounted volumes
When there is only one volume mounted
When there are many volumes
When the a volume contains whitespaces

First Cycle
Parse the output of “df” process
When there are no volumes
When there is only one volume

@Test
public void whenNoVolumes() {
String input = "Filesystem 1024-blocks Used Available Capacity
Mounted on”;
List<String> result = parseDfOutput(input);
assertEquals(emptyList(), result);
}

@Test
Mounted on”;
}
private List<String> parseDfOutput(String string) {
return null;
}

@Test
Mounted on”;
}
return emptyList();
}

Second Cycle

@Test public void whenOneVolume() {
List<String> result = parseDfOutput(""
+ "Filesystem 1024-blocks Used Available Capacity Mounted
onn"
+ "/dev/disk0s2 243862672 135479924 108126748 56% /");
assertEquals(asList("/"), result);
}

return emptyList();
}

List<String> result = new ArrayList<String>();
return result;
}

private List<String> parseDfOutput(String input) {
Scanner scanner = new Scanner(input);
scanner.nextLine(); // skip header
if(scanner.hasNextLine()) {
String line = scanner.nextLine();
Scanner scanner1 = new Scanner(line);
scanner1.next(); // skip Filesystem
scanner1.next(); // skip 1024-blocks
scanner1.next(); // skip Used
scanner1.next(); // skip Available
scanner1.next(); // skip Capacity
String mountPoint = scanner1.next();
result.add(mountPoint);
}
return result;
}

Scanner lines = new Scanner(input);
lines.nextLine(); // skip header
if(lines.hasNextLine()) {
String line = lines.nextLine();
Scanner values = new Scanner(line);
values.next(); // skip Filesystem
values.next(); // skip 1024-blocks
values.next(); // skip Used
values.next(); // skip Available
values.next(); // skip Capacity
String mountPoint = values.next();
}
return result;
}

result.add(parseMountPoint(lines.nextLine()));
}
return result;
}
private String parseMountPoint(String line) {
Scanner values = new Scanner(line);
values.next(); // skip Filesystem
values.next(); // skip 1024-blocks
values.next(); // skip Used
values.next(); // skip Available
values.next(); // skip Capacity
String mountPoint = values.next();
return mountPoint;
}

Third Cycle

@Test public void whenMultipleVolume() {
List<String> result = parseDfOutput(""
+ "Filesystem 1024-blocks Used Available Capacity Mounted
onn"
+ "/dev/disk0s2 243862672 135479924 108126748 56% /n"
+ "/dev/disk0s2 243862672 135479924 108126748 56%
/media/diskn"
+ "/dev/disk0s2 243862672 135479924 108126748 56%
/tmpn");
assertEquals(asList("/", "/media/disk", "/tmp"), result);
}

String mountPoint = parseMountPoint(line);
}
return result;
}

while(lines.hasNextLine()) {
String mountPoint = parseMountPoint(line);
}
return result;
}

TDD Rules
Test First
Test for All Features
Remove all duplication
(always)

Some hints
Keep tests running and passing
Keeps test small
Don’t mix phases (Red, Green,
Refactor)
Don’t mix unit tests with integration
tests
Test only one feature per test

Regole applicate
Ogni feature deve essere sviluppata secondo il
TDD
Partire dai test di accettazione
Ritardare le decisioni di design all’ultimo
momento responsabile
Applicare un principio di design solo dopo aver
avuto la prova che sia utile in quel specifico caso

Prima feature: produrre
testo pronunciabile

Test di accettazione
public class HoroscopeTest {
@Test public void
userListenOroscope() {
Horoscope horoscope = new Horoscope();
horoscope.saveDivination("22-GIU-10", "Ariete",
"Sarai molto fortunato.");
String result =
horoscope.GET("/horoscope/ariete.txt");
assertEquals("22 giugno 2010: Ariete, Sarai
molto fortunato.”, result);
}

No test  No code
Quando scrivo il codice di produzione scrivo il
minimo necessario a far passare il test
Se il minimo non mi convince (è troppo stupido),
vuol dire che manca una specifica funzionale 
cioè manca un test.
Prima di scrivere una qualsiasi riga di codice in
più aggiungo un test che la richieda.

@Test public void
shouldStoreDivinationsForMultipleSigns() {
Horoscope horoscope = new Horoscope();
"for ariete");
horoscope.saveDivination("22-GIU-10", "Toro",
"for toro");
assertEquals("22 giugno 2010: Ariete, for ariete",
horoscope.GET("/horoscope/ariete.txt"));
assertEquals("22 giugno 2010: Toro, for toro",
horoscope.GET("/horoscope/toro.txt"));
}

Cerco di non anticipare il
design
Prima di affrontare lo sviluppo faccio una veloce sessione
di design
Non implemento nessuna decisione fino a che non si
rende necessaria
E.g. anche servirà un DAO per adesso salvo tutto in RAM

Seconda Feature:
oroscopo ascoltabile

@Test public void howToCreateMp3() {
Horoscope horoscope = new Horoscope(
aFakeSyntetizerWhichReturns(
aMp3Stream()));
"divination");
assertThat(horoscope.GET(
"/horoscope/ariete.mp3").asByteArray(),
is(equalTo(aMp3Stream())));
}

Resource
Ora il GET restituisce una Resource
 public Resource GET(String path) {...}
Il client decide quale rappresentazione usare:
horoscope.GET("/horoscope/ariete/divination.txt").asString());
horoscope.GET("/horoscope/ariete/divination.mp3").asByteArray();

Stato delle cose
Al momento tutto viene persistito in memoria (in una
HashMap)
Non esiste ancora un oggetto DAO, tutto viene fatto
dall’unica class Horoscope

Estrazione del comportamento
public class MemoryDivinationRepo {
Divination lastDivinationForSign(String sign);
void saveDivinationFromPronounce(String sign,
String pronounce);
};
public interface Divination {
String asText();
byte[] asMp3();
};

Estrazione dell’interfaccia
public class MemoryDivinationRepo
implements DivinationRepo {...}
public interface DivinationRepo {
Divination lastDivinationForSign(String sign);
void saveDivinationFromPronounce(String sign,
String pronounce);
};

Caratterizzazione del
comportamento
L’interfaccia è una minima parte del contratto, la parte
più importante è il comportamento che l’oggetto
dovrebbe avere.
Il comportamento lo estraggo con dei test di
caratterizzazione

Caratterizzazione di
MemoryDivinationRepo
public class MemoryDivinationRepoTest {
@Test public void
shouldStoreDivinationPronounceForASign() {...}
@Test public void
shouldReplyWithAPronouncedMp3() {...}
@Test public void
shouldStoreDivinationPronounceForMultipleSigns()
{...}
@Test public void
shouldOverrideDivinationPronounce() {...}
}

Thanks
Andrea Francia
www.andreafrancia.it
blog.andreafrancia.it
andrea@andreafrancia.it

Example of an Automated Test
@Test public void shouldParsePath() {
String content =
"[Trash Info]n"
+ "Path=/home/andrea/foo.txtn"
+ "DeletionDate=2010-08-23T12:59:14n";
String path = Parser.parsePath(content);
assertEquals("/home/andrea/foo.txt”,
path);
}

Testing Frameworks
http://en.wikipedia.org/wiki/List_of_unit_testing_frameworks
•PHPUnit
•SimpleTest
•Google C++ Testing Framework
•CppUnitLite
•CppUnit
•JUnit
•TestNG
•PyUnit
•Nose

Introduzione al TDD

More Related Content

What's hot

Viewers also liked

Similar to Introduzione al TDD

More from Andrea Francia

Recently uploaded

Introduzione al TDD

Editor's Notes