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

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (19)

Destacado

Destacado (12)

Similar a Introduzione al TDD

Similar a Introduzione al TDD (20)

Más de Andrea Francia

Más de Andrea Francia (12)

Último

Último (20)

Introduzione al TDD

Notas del editor