Test Driven Development Introduction

Test Driven Development Introduction

Issued date: 8/29/2007Author: Nguyen Phuc Hai

Agenda

Introduction Unit test overview Refactoring Test Driven Development approach Q&A

Trainer’s profile

Over seven years experienced in software industry on both product development and out-sourcing.

Hand-over various positions from developers, technical lead, project manager, technical architecture and program/product managers.

Trainer’s profile (cont.)

Be experienced in managing small, medium and large projects/program – Took oversight more than 100 associates in one of the biggest account in company

Be experienced on technical design, technical management in various sizes of projects from small to enterprise applications on both desktop and web environment

Trainer’s profile

Be recognized as an Agile expert that has experienced in managing Agile process, applying Agile practices.

Maintain the blog that share experienced in software development on both technical and management areas (http://www.haiphucnguyen.net/blog/)

Unit test key ideas

Unit test - FAQs

Check the link for some common concerns of applying unit test and its benefits: http://www.haiphucnguyen.net/blog/?p=40

Unit test best practices

Keep test method as simple as possible:– DRY principle (Don’t repeat yourself)– Re-use test set up across test cases: put non-

trivial test data in test set up method– Clean test code as productive code

Evident data All non-trivial methods must be passed unit

test with 100% coverage ratio.

Unit test best practices

Unit test independent with:– Other unit tests, order of unit test running– Environment (operating system, hardware

configuration, database …) Fix broken test as soon as possible (it should

be immediately) After fixing defect, write unit test to prevent it

re-occur

Unit test best practices

All test cases must be passed at the end of working day.

Test project code, not library code Minimal maintenance of test code If you can not write unit test for some

functionality that means your code has problem! Refactor it immediately

How to make code becomes testable

Using interface in communication among layers, modules.

Dependency injection Dependency lookup Methods/Constructors has as less

parameters as possible (4 is the best number)

How to make code becomes testable

Class is not depended in many other classes -> it is hard to initiate instance of this class

One method has only one purpose Be careful with singleton class or static

methods! And the most important: refactoring your

code if it is not testable (esp. legacy code)

Refactoring

Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring.

Refactoring (cont.)

Whenever you think you can make more benefits with your new code:– Increase the re-usability– Make the code becomes testable– Avoid the rigid, fragile issues– Better performance– …

Refactoring – best practices

Keep small change running before proceed another change.

Unit test should be written to make sure refactoring does not change system’s behaviors.

To legacy system: write test first, refactoring and verify result

Test Driven Development

TDD is a technique to improve the quality of both code and design. Developers will write the test first, then writing the code to make it pass the test. They can refactor code to avoid issues (duplication or non-optimize code …)

TDD benefits

Promoting high code coverage for productive code.

Improving quality of architecture and code Prevent defects cost is less than detect

defects cost

TDD Cycle

Prepare a list of test cases Follow the TDD Rhythm:

– Pick a test to implement– Write a fail test– Quickly make test green– Refactor to eliminate duplication

TDD – Things always do

Write test-first Maintain to-do list Writing new code only if there is failing

automated test Run all tests all the time not only single

isolated test

TDD – Things always do

Job is done whenever complete implementation and all test have green status

TDD – Things never do

Write test for trivial methods (such as getters/setters)

Commit code with failed test Big upfront design and code that makes test

first do not cover all cases of writing code

TDD best practices

Write the simple test first, then write code. After that write test code for more complexity functionality

Run test immediately whenever complete writing code

If spending much time for writing code, break the functionality into smaller ones and applying TDD for these pieces

TDD best practices

Whenever test code or productive code smells, refactor it immediately

After writing code, use coverage tool to make sure productive code is covered 100% by test method. If some piece of code is not covered, your implementation has problem!

Use mock objects if needed

Tools support TDD

Various tools help developers easier to do TDD:– IDE: Eclipse, MS Visual Studio Team System– Build tools: Ant, Maven, Nant– xUnit tools: Junit, TestNG, DBUnit, Nunit, …– Coverage tools: JCoverage, NCoverage

TDD examples

A user story of login page:– Presentation Layer: Login.html, Login.java– Service Layer: LoginService.java– Data Access Layer: LoginDAO.java

More complex user story: applying acegi for authentication – authorization process:– Re-factor LoginService.java– Run test again

TDD examples (cont.)

Write the mock up html file: Login.html Write test class: LoginTest.java Write test method for case user login

success:@TestPublic void testLoginSuccess() { ….}

TDD examples (cont.)

Implement login function that pass the testVoid onSubmit() { if (username.equals(“VietNam”)) { setResponsePage(Helloworld.class); } else { form.error(“Login fail”); }}

TDD examples (cont.)

Run LoginTest again and verify result (it has green color)

Return the Login.java and add feature verifying user base on databaseVoid onSubmit() { if (userService.getUser(userName) != null) { … }}

TDD examples (cont.)

The enterprise application that maintains the suite of test cases and number of test cases is growing daily:– Automation unit test– Continuous Integration

TDD examples (cont.)

TDD examples (cont.)

Q&A

Any question of unit test, refactoring and TDD is welcome

Thank you

I hope you enjoy with this course. Any further discussion, please contact me at– Email: [email protected]– My blog: http://blog.esofthead.com