Introduction to Software Testing

“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

Getting feedback,
as much frequent as we can

Taxonomy
Scope
Unit
Integration
System
Visibillity
Black box
White box
Intention
Acceptance
Functional
Non Functional
…
Technique
Static
Dynamic
Execution
Automatic
Manual

Visibillity
Black
box
White
box
System
Integration
Unit
Intention
Acceptance
Functional
Non
Functional
Technique
Dynamic
Static

Scope
Database
PORT1 PORT2
ADAPTER1

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.

• 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.

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

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();
validate: validatorSpy;
}
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();
validate: validatorSpy;
}
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

Integrationtestwhichwanttobeunittests
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

Integrationtestwhichworkswithexternalsystem
Database

IntegrationtestwhichusestheUI
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

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 another
4. 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]))
}
...

a
b c
d
…x
...
errors = []
}
}
...

edges – nodes + 2 = predicate nodes +1 = number of regions
a
b c
d
…x
...
errors = []
}
}
...

Black box (partitioning)
1. Identify equivalence classes
2. Select dataset:
1. Assign a unique value for every class
2. Select tests cases which cover the most
valid classes
3. Select tests cases which cover only one
invalid class at the same time

Register
Username*
Password (6-10 chars including numbers)

Register
Username*
Username Password
U1: myNick P1: p4ssw0rd
U2: “empty” P2: p4ss
P3: l4rg3p4ssw0rd
P4: password

Register
Username*
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

4 phases-tests
1.Set Up
2.Exercise
3.Verify
4.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
@Before
public void setUp() {
this.userValidator = mock(UserValidator.class);
this.userDao = mock(UserDao.class);
this.userService = new UserService(userValidator, userDao);
}
@Test
public 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"));
}
@After
public 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(){
})
it('should call dao', function(){
})
afterEach(function(){
// clean the state
})
})
})

BDD (specification)
Feature: User registration
Scenario: 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 created
Example:
| 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) {
...
}

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

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
…

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 Project
MyIOSProject/
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

¿Couldyoube able to rewrite the codeonly
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 { ... }
VS
public void validateUserWithNoPasswordShouldThrowsError { ... }
com.mycompany.artifactId.it.TestSteps ...
VS
com.mycompany.artifactId.it.usermanagement.UserCreationSteps ...

IspendmoretimewritingcodetosetupmySUTthan
writingthetest,howdo you solveit?
• Read about Fixtures (Xunit Patterns is a
good reference)
• Fresh fixtures
• Shared fixtures
• Persistent fixtures

Iduplicatetoomuchcodeonobjectscreation,mocks
definitionandassertion…
• 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();
VS
User user = new User("irrelevantUsername", "v4l1dP4ss", irrelevant@myCompany.com", ...);
assertNotNull(user.getUsername());
assertNotNull(user.getPassword());
assertNotNull(user.getEmail());
...
VS
assertContainsAllMandatoryData(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
pattern
• Mocks aren’t Stubs
• Misko Hevery blog
• http://refactoring.com/
• …

Introduction to Software Testing

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