Workshop for developers: save ourselves with unit testing :)

Stefano Ottaviani

XPUG Marche & DevMarche

About MeContacts

Stefano Ottaviani

steott@gmail.com

@ste8

Arcevia (AN) - Italy

Communities

DevMarche

XPUG Marche

DotNetMarche

UgiDotNet

DDD / CQRS

Work

Sales Force Automation

Warehouse logistic

Mobile

MonoTouch

About You Who usually write tests?

Who knows about tests?

Tests? What??

Our Mission

Spread testing practices among

developers

as a basic skill of professional developers

A first major mistake people make is thinking that the testing team is responsible

for assuring quality.

Brian Marick

Why software testing?And why automate it?

1. Bug detection

reduce bugs in production code

Is it "only" that?

Exercise:Let’s introduce unit testing!

String Calculator Kataby Roy Osherove

Unit test definition

by Roy Osherovehttp://artofunittesting.com/definition-of-a-unit-test/

A unit test is an automated piece of code that invokes a unit of work

in the system and then checks a single assumption about the

behavior of that unit of work.

Unit test definitionby Roy Osherove

A unit of work is a single logical functional use case in the system that can be invoked by some public

interface (in most cases).

Unit of work definition (1/2)

by Roy Osherove

A unit of work can span a single method, a whole class or multiple

classes working together to achieve one single logical purpose that can

be verified.

Unit of work definition (2/2)

by Roy Osherove

A good unit test is: (1/2) by Roy Osherove

Able to be fully automated Has full control over all the pieces running (use mocks or stubs to achieve this isolation when needed)

Can be run in any order if part of many other tests

Runs in memory (no DB or File access, for example)

Runs fast

A good unit test is: (2/2) by Roy Osherove

Consistently returns the same result (you always run the same test, so no random numbers or DateTime.Now, for example. Save those for integration or range tests)

Tests a single logical concept in the system Readable Maintainable Trustworthy (when you see its result, you don’t need to debug the code just to be sure

Some benefits…

2. Faster development without debugging

no F5, login, go to the form, input data, …

3. Regression test-suite

add features without breaking the old ones

4. Instant, visual feedback

automated tests can be run as frequently as required

5. Refactoring

improve the design without breaking ithttp://xpugmarche.blogspot.it/2009/04/2-meeting-sessione-di-refactoring.html

White boxvs

Black box

testing

White box testing Tester knows about internals and exploit that knowledge

Based on code analysis Statement coverage Branch coverage Condition coverage Basis path coverage => Cyclomatic complexity

Black box testing Tester does not know anything about the test object internal

Focuses on functional requirements

Based on input domain analysis Equivalence partitioning

Boundary value analysis

Equivalence partitioning (1/2)

A method having 4 integer input parameters with a 16-bit representation has an input domain of 264 different values => 264 different test cases

Equivalence partitioning is a black box testing method that divides the input domain of a program into classes of data from which test cases can be derived.

If an input condition specifies a range, one valid and two invalid equivalence classes are defined (invalid1 [--valid--] invalid2)

Equivalence partitioning (2/2)

If an input condition requires a specific value, one valid (==) and two invalid (<, >) classes are defined.

If an input condition specifies a member of a set, one valid and one invalid equivalence class are defined.

If an input condition is boolean, one valid and one invalid class are defined

Boundary value analysis (1/2)

Boundary value analysis is a test case design technique that complements equivalence partitioning.

In fact, a greater number of errors occurs at the boundaries of the input domain rather than in the "center".

The reason is that developers often concentrate on ordinary values and ignore "marginal" values.

Boundary value analysis (2/2)

If an input condition specifies a range bounded by values a and b, test cases should be designed with values a and b as well as just above and just below a and b.

If an input condition specifies a number of values, test cases should be developed that exercise the minimum and maximum numbers. Values just above and below minimum and maximum are also tested.

If internal data structures have prescribed boundaries, be certain to design a test case to exercise the data structure at its boundary.

6. Less "thinking" about boundary conditions

collections’ indexes, date ranges, …

Exercise:Boundary Conditions

Reservations list

Code coverage

Should I test 100% of my code?

Naming conventions and structure

Roy Osherove Way

Method: UnitOfWork_ScenarioUnderTest_ExpectedBehavior

public void Sum_simpleValues_Calculated ()

public void Sum_NegativeNumberAs1stParam_ExceptionThrown()

public void IsLoginOK_UserDoesNotExist_ReturnsFalse ()

http://osherove.com/blog/2005/4/3/naming-standards-for-unit-tests.html

http://osherove.com/blog/2012/5/15/test-naming-conventions-with-unit-of-work.html

The Art of Unit Testing (book)

AAA – Arrange, Act, Assert

Nested class per methodhttp://haacked.com/archive/2012/01/01/structuring-unit-tests.aspx

Class Test Fixture

Exercise:Let’s introduce

integration testing!

Events Webservice

Exercise:mocks and stubs

Price Calculator

Mocks: record and verify expectations

Stubs: do not verify expectations

Mocks aren’t StubsBy Martin Fowler

http://martinfowler.com/articles/mocksArentStubs.html

Database integration strategies

Use of in-memory db such as Sqlite => NO GOOD!

Use of Transactions => less problemshttp://osherove.com/blog/2013/3/28/using-systemtransactionstransactionscope-to-rollback-databas.html

Libraries such as NDbUnit

Recap: http://lostechies.com/jimmybogard/2012/10/18/isolating-database-data-in-integration-tests/

Some other benefits…

7. No need to wait development of other components

(database tables, web services …)

thanks to Dependency Injection

8. Better design

modularization, lower coupling,

SRP (Single responsibility principle)

A possible tests classification

Unit testing

Integration testing

Validation testing: acceptance (end-to-end), alpha, beta, …

System testing: security, stress, recovery, …

Caveat emptor

No formal proof of correctness

you can't be sure to catch all errors

Testing can never completely establish the correctness of arbitrary

computer software

Testing shows the presence,

not the absence of bugs.

Edsger W. Dijkstra

Beware of bugs in the above code;

I have only proved it correct, not tried it.

Donald Knuth

Pitfalls of (bad) testsfragile, slow, do not test actual features

The Magic Tricks of Testing by Sandi Metz

http://bit.ly/ZwV4U3

@nusco said: after 12+ years of TDD, @sandimetz changed the way I conceptualize it

Setup & Teardown

To Use or Not to Use?

http://jamesnewkirk.typepad.com/posts/2007/09/why-you-should-.html

http://agileprogrammer.com/2005/07/23/assiduously-avoid-setup-and-teardown/

9. Companion of code reviews

"Classic" unit tesingvs

Test Firstvs

Test Driven Development - TDD

Test First Same attitude of bug reproduction: first, put yourself in the "broken" situation

Who wants to write tests after code?

TDD Test Driven Development

More on design than testing!

[ITA] Piergiuliano Bossi course on Youtube: http://bit.ly/1bPw9D7

10. No writer block

specially with TDD

11. Gain a client perspective

on how we should model

12. Form of sample code and documentation

used by many open source libraries

13. Continuous Integration

automated build including tests to detect errors as quickly as possible.

All these brings to…

14. Confidence…

15. …fun and satisfaction!

And tomorrow?Where do I start?

Will the boss permit… ?

Test on languageswith dynamic typing(e.g. javascript)

Compilers are a kind of test!

XP and testing

Benefits Recap (1/2)

1.Bug detection

2.Faster development without debugging

3.Regression test-suite

4.Instant, visual feedback

5.Refactoring

6.Less "thinking" about boundary conditions

7.No need to wait development of other components (database, ...)

Benefits Recap (2/2)

8.Better design

9.Companion of code reviews

10.No writer block

11.Gain a client perspective

12.Form of sample code and documentation

13.Continuous Integration

14.Confidence

15.Fun and satisfaction

Some resources (1/2)

[ITA] "Unit Tests VS End to End Tests" (Domenico Musco) https://vimeo.com/33150685

"Magic Tricks of Testing" (Sandi Metz) http://bit.ly/ZwV4U3

@nusco said: after 12+ years of TDD, @sandimetz changed the way I conceptualize it

[ITA] TDD course by Piergiuliano Bossi: http://bit.ly/1bPw9D7

Some resources (2/2)

The Art of Unit Testing with Examples in .NET, 2nd Edition (Roy Osherove) http://www.slideshare.net/royosherove/talk-2ndlookunittesting-copy

GOOS - Growing Object-Oriented Software Guided by Tests (Steve Freeman and Nat Pryce)

Test Driven Development By Example (Kent Back)