Introduction to Software Testing

TestingA brief introduction

Main concepts

“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 …”

Kent Beck

No silver bullets

What is testing about?

Getting feedback,as much frequent as we can

the sooner, the better

TAXONOMY

Taxo

nom

yScope

Unit

Integration

System

VisibillityBlack box

White box

Intention

Acceptance

Functional

Non Functional

…

TechniqueStatic

Dynamic

ExecutionAutomatic

Manual

Visibillity

Black box

White box

System

Integration

Unit

Intention

Acceptance

Functional

Non Functional

Technique

Dynamic

Static

Scope

Database

PORT1 PORT2

ADAPTER1

Unit test

Database

Dependency injection

•Dependency:A depends on B when A needs B to do its job.• Injection:

Object which uses A tells A who is B.

Dependency injection

• Separate business logic from creation logic• Avoid use of new for service objects.• Value objects can be created any where.

• Service objects in charge to implement business logic.• IOC Container or factories in charge of creation

logic.

Dependency injection

public UserService(UserValidator userValidator, UserDao userDao) {this.userValidator = userValidator;this.userDao = userDao;

}

public User createUser(User user) throws ValidationException {

this.userValidator.validate(user);

user = this.userDao.create(user); return user;}

public User createUser(User user) throws ValidationException {

UserValidator userValidator = new UserValidator(...);

userValidator.validate(user);

UserDao userDao = new UserDao(...);

user = userDao.create(user);return user;

}

VS

Dependency injection

public UserService(UserValidator userValidator, UserDao userDao) {this.userValidator = userValidator;this.userDao = userDao;

}

public User createUser(User user) throws ValidationException {

this.userValidator.validate(user);

user = this.userDao.create(user); return user;}

public User createUser(User user) throws ValidationException {

UserValidator userValidator = new UserValidator(...);

userValidator.validate(user);

UserDao userDao = new UserDao(...);

user = userDao.create(user);return user;

}

VSthis sucks

Test doubles

•Fake•Stub•Spy•Mock

Test doubles (Fake)

public UserDaoFake implements UserDao { @Override public User create(User user) { return new User(...); }}

Fake implementation in order to make test pass.

Test doubles (Stub)

UserValidator validatorMock = mock(UserValidator.class);

stub(validatorMock.validate(any(User.class))).toThrow(new ValidationException());

var validateCall = Sinon.stub();validatorStub.withArgs(user) .onFirstCall().returns(validationError);

var userValidator = { validate: validatorStub;}

OR WITH JS

Stubs provide canned answers to calls made during the test, usually not responding at all to anything outside what’s programmed in for the test.

Test doubles (Spy)Spies are objects that also record some information based on how they were called

var validatorSpy = Sinon.spy();var userValidator = { validate: validatorSpy;}userValidator.validate(user);sinon.assert.calledOnce(validatorSpy);sinon.assert.calledWith(validatorSpy, user);

OR WITH JS

UserValidator validatorSpy = spy(new UserValidator());doThrow(new ValidationException()).when(validatorSpy).validate();verify(validatorMock).validate(any(User.class))

Test doubles (Spy)Spies are objects that also record some information based on how they were called

var validatorSpy = Sinon.spy();var userValidator = { validate: validatorSpy;}userValidator.validate(user);sinon.assert.calledOnce(validatorSpy);sinon.assert.calledWith(validatorSpy, user);

OR WITH JS

UserValidator validatorSpy = spy(new UserValidator());doThrow(new ValidationException()).when(validatorSpy).validate();

Test doubles (Mocks)

UserValidator validatorMock = mock(UserValidator.class);when(validatorMock.validate(any(User.class))).thenTrhow(new ValidationException());

verify(validatorMock).validate(any(User.class))

Informal: think in a Stub which is also a Spy. It also responds with default values to non-explicitly declared methods

var validatorAPI = {validate: function()};var validatorMock = Sinon.mock(validatorAPI);validatorMock.expects('validate').once() .withArgs(user).throws(validationError)validatorAPI.validate(user)validatorMock.verify()

OR WITH JS

Integration test which want to be unit tests

Database

FIRST(IT)• Fast

Hundreds or thousands per second• Isolates

Failure reasons become obvious• Repeatable

In any order, any time• Self-validating

No manual execution required• Timely

Written before code• Immutable*

SUT is in the same state after execute the tests• Trusted*

When the test fails, the system fail and when the test works, the system works

Integration test which works with external system

Database

Integration test which uses the UI

Database

System test

Database

Who, when and where run the tests?

• Unit• Owner: developer• When: after every change• Where: every computer

• Integration• Owner: developer || QA team• When: as part or after commit stage• Where: devel and pre-pro environments

• System• Owner: QA team• When: as part or after commit stage• Where: devel and pre-pro environments

STRATEGIES

Static evaluation

• Informal review• Formal review (inspection)•Checklists• Sucessive abstraction•Walkthrough

Dynamic evaluation

• White box• Path Coverage• Statement Coverage• Condition Coverage• Function Coverage

• Black box• Equivalence partitioning• Boundary values analysis

White box (*-coverage)1. Get flow diagram of the SUT

2. Calculate cyclomatic complexity

3. Determine a data set which force going one path or another4. Exercise the SUT with this dataset.

...errors = []

if (user.name ==null || user.email == null) {

errors.push('mandatory fields not found');}//do the rest of whatever

for (var i=0; i < user.friends ; i++) { errors.push(checkFriendShipt(user.friends[i]))}...

White box (*-coverage)1. Get flow diagram of the SUT

2. Calculate cyclomatic complexity

3. Determine a data set which force going one path or another4. Exercise the SUT with this dataset.

a

b c

d

…x

...errors = []

if (user.name ==null || user.email == null) {

errors.push('mandatory fields not found');}//do the rest of whatever

for (var i=0; i < user.friends ; i++) { errors.push(checkFriendShipt(user.friends[i]))}...

White box (*-coverage)1. Get flow diagram of the SUT

2. Calculate cyclomatic complexity

3. Determine a data set which force going one path or another4. Exercise the SUT with this dataset.

edges – nodes + 2 = predicate nodes +1 = number of regions

a

b c

d

…x

...errors = []

if (user.name ==null || user.email == null) {

errors.push('mandatory fields not found');}//do the rest of whatever

for (var i=0; i < user.friends ; i++) { errors.push(checkFriendShipt(user.friends[i]))}...

Black box (partitioning)

1. Identify equivalence classes2. Select dataset:

1. Assign a unique value for every class2. Select tests cases which cover the most

valid classes3. Select tests cases which cover only one

invalid class at the same time

Black box (partitioning)

Register

Username*

Password (6-10 chars including numbers)

Black box (partitioning)

Register

Username*

Password (6-10 chars including numbers)

Username Password

U1: myNick P1: p4ssw0rd

U2: “empty” P2: p4ss

P3: l4rg3p4ssw0rd

P4: password

Black box (partitioning)

Register

Username*

Password (6-10 chars including numbers)

Username Password

U1: myNick P1: p4ssw0rd

U2: “empty” P2: p4ss

P3: l4rg3p4ssw0rd

P4: password

Test Cases myNick, p4ssw0rd √ myNick, p4ss X myNick, l4rg3p4ssw0rd X myNick, password X “empty”, p4ssw0rd X

AUTOMATIC TESTING

4 phases-tests

1. Set Up2. Exercise3. Verify4. TearDown

Testing frameworks families• X-Unit• @Before(Class)• @Test• @After(Class)

• Rspec• describe

• beforeEach• it• afterEach

• Specification by example (A.K.A BDD)• Given• When• Then

XUnit@Beforepublic void setUp() { this.userValidator = mock(UserValidator.class); this.userDao = mock(UserDao.class); this.userService = new UserService(userValidator, userDao);}

@Testpublic void createValidUserShouldNotFail() { //Exercise User expectedCreatedUser = new User("irrelevantUser"); when(userValidator.validate(any(User.class))); when(userValidator.validate(any(User.class))).thenReturn(createdUser); User createdUser = userService.create(new User()); //Assertions assertThat(createdUser, equalTo(expectedCreatedUser));}

@Test(expected=ValidationException)public void createInvalidUserShouldFail() { when(userValidator.validate(any(User.class))) .thenReturn(new ValidationException()); userService.create(new User("irrelevantUser"));}

@Afterpublic void tearDown() { //clean the state here}

Rspec (suite per class)describe('UserService test suite:', function(){ beforeEach(function(){ // setup the SUT })

it('when create a valid user should not fail', function(){ // exercise + assertions })

it('when create an invalid user should fail', function(){ // exercise + assertions })

afterEach(function(){ // clean the state })})

• UserService test suite:• When create a valid user should not fail √• When create an invalid user should fail √

The report will look like:

Rspec (suite per setup)describe('UserService test suite:', function(){ describe("when create a valid user ", function() { beforeEach(function(){ // setup and exercise })

it('should return valid user', function(){ // partial assertions })

it('should call validator', function(){ // partial assertions })

it('should call dao', function(){ // partial assertions })

afterEach(function(){ // clean the state })

})})

BDD (specification)Feature: User registrationScenario: User tries to register sending valid data so the system will create new account Given the user has introduced <username> and <password> into the registration form And has accepted terms and agreements When send the registration from Then the user with <username> should be createdExample: | username | password | | myNick | p4ssw0rd |

Scenario: User tries to register sending invalid data so the system will reject user Given the user has introduced <username> and <password> into the registration form And has accepted terms and agreements When send the registration from Then the system should notify <error>Example: | username | password | error | | myNick | p4ss | password should have at least 6 characters | | myNick | l4rg3p4ssword | password should have at less than 10 characters | | myNick | password | password should contains at least a number | | | p4ssword | username is mandatory |

BDD(implementation)@given("the user has introduced (\w)+ and (\w)+ into the registration form")public void populateForm(String username, String password) { ...}

@given("has accepted terms and agreements")public void acceptTerms() { ...}

@when("send the registration from")public void sendRegistrationForm() { ...}

@then("the user with (\w)+ should be created")public void verifyUserIsCreated(String username) { ...}

@then("the system should notify <error>")public void verifyErrors(String error) { ...}

TESTABLE DESIGN

Non-Testable design smells (by Misko Hevery*)

•Constructors does Real Work•Digging into collaborators•Brittle Global State & Singletons•Class Does Too Much Work

*See http://misko.hevery.com/attachments/Guide-Writing%20Testable%20Code.pdf

Constructors does Real Work

• new keyword in a constructor or at field declaration • Static method calls in a constructor or at field declaration • Anything more than field assignment in constructors • Object not fully initialized after the constructor finishes

(watch out for initialize methods) • Control flow (conditional or looping logic) in a

constructor • CL does complex object graph construction inside a

constructor rather than using a factory or builder • Adding or using an initialization block

Digging into collaborators

• Objects are passed in but never used directly (only used to get access to other objects) • Law of Demeter violation: method call chain

walks an object graph with more than one dot (.) • Suspicious names: context, environment,

principal, container, or manager

Brittle Global State & Singletons

• Adding or using singletons • Adding or using static fields or static

methods • Adding or using static initialization blocks • Adding or using registries • Adding or using service locators

Class Does Too Much Work

• Summing up what the class does includes the word “and” • Class would be challenging for new team

members to read and quickly “get it” • Class has fields that are only used in some

methods • Class has static methods that only operate on

parameters

Questions & Stupid questions• ¿Where I place my tests?• ¿Who tests the classes which test our classes?• ¿Could you be able to rewrite the code only reading the tests

definitions?• I spend more time writing code to setup my SUT than writing

the test, how do you solve it?• ¿What is the minimum coverage should I expect for my code?• I’ve never write a test ¿where can I start?• My code is not testable at all, ¿what can I do?

¿Where I place my tests?

• Unit tests:• Test Class per Class• Test Class per SetUp (useful in Xunit frameworks)• Important naming convention (<ClassName>Test,

<TestSuite>IntegrationTest, …)• System tests:• Different project

¿Where I place my tests?Java Project (Test Class per Class) MyProject/ src/ main/ java/ com.groupId.artifactId.MyClass.java resources/ test/ java/ com.groupId.artifactId.MyClassTest.java com.groupId.artifactId.it.suite.MyTestCaseIntegrationTest.java resources/

NodeJs Project MyProject/ lib/ myClass.js main.js test/ ut/ /suite it/ lib/ myClassTest.js

Java Project (Class per SetUp) MyProject/ src/ main/ … test/ java/ com.groupId.artifactId.myclass.<SetUp1>Test.java com.groupId.artifactId.myclass.<SetUp2>Test.java …

¿Where I place my tests?Android Project MyProject/ AndroidManifest.xml res/ ... (resources for main application) src/ ... (source code for main application) ... tests/ AndroidManifest.xml res/ ... (resources for tests) src/ ... (source code for tests)

IOS ProjectMyIOSProject/ MyIOSProject/ ... app code ... MyIOSProjectTests/ ... test code ...

¿Who tests the classes which test our classes?

• Exactly, this is why it’s so important our tests follow

KISS

¿Could you be able to rewrite the code only reading the tests definitions?

• Tests (specially Black Box tests) should tell us an story.

• Use descriptive name methods for unit tests:

• User well defined, and complete scenarios for system tests:• Use business vocabulary for acceptance tests:

public void testValidaterUser1 { ... }

VSpublic void validateUserWithNoPasswordShouldThrowsError { ... }

com.mycompany.artifactId.it.TestSteps ...

VScom.mycompany.artifactId.it.usermanagement.UserCreationSteps ...

I spend more time writing code to setup my SUT than writing the test, how do you solve it?

• Read about Fixtures (Xunit Patterns is a good reference)• Fresh fixtures• Shared fixtures• Persistent fixtures

I duplicate too much code on objects creation, mocks definition and assertion…

• Writing a lot of code to initialize value objects?• Create DataBuilders

• Writing a lot of code to initialize mock/stub objects?• Create MockBuilders

• Writing a lot of asserts (more purist says only one assertion)?• Create CustomAsserts

User user = userDataBuilder.createValidUser();

VSUser user = new User("irrelevantUsername", "v4l1dP4ss", irrelevant@myCompany.com", ...);

assertNotNull(user.getUsername());assertNotNull(user.getPassword());

assertNotNull(user.getEmail());...

VSassertContainsAllMandatoryData(user);

¿What is the minimum coverage should I expect for my code?• It depends on the project.• “… test as little as possible to reach a given level

of confidence …”• Do not get obsess over test coverage, it’s a

metric, not a goal.

I’ve never write a test ¿where can I start?

Database

PORT1 PORT2

ADAPTER1

I’ll bet you a beer , you

called it *Util…

My code is not testable at all, ¿what can I do?• First of all, go to http://refactoring.com/• I suggest:

1. Add integration regression test.2. Remove new from methods and ad it to constructors (this will

prepare your class for dependency injection).3. Creates a constructor which receive every dependency your

class will need.4. Remove static classes and methods (adding the new non-static

as a class dependency).5. Add as much tests as you want to ;)

Important!!! Do it step by step

Recommended reading• Growing Object Oriented Software Guided Tests• Xunit Patterns• Continuous delivery• Hexagonal Architecture• Inversion of Control Container and the Dependency Injection p

attern• Mocks aren’t Stubs• Misko Hevery blog• http://refactoring.com/• …

Q&APlace your question here!