Test Driven Development
with %UnitTest

Marc Stober

Software Engineer, Partners HealthCare

Presentation to NEMUG, November 13, 2012

Who am I?

Came to Partners about 5 years ago as an OO developer on Microsoft stack
Caché is pretty cool!
Past contributor to MbUnit
Disclaimer: This presentation represents my experience as a developer,
not the official policy of my employer.

TO DO TDD WITH %UnitTest

Image source: Wikipedia

unit test /YOO-nit test/ noun

Small scale tests
Testing that uses JUnit-like (xUnit) tools (any scale)
Test Driven Development

A short history...

~1992: Kent Beck first implemented in SmallTalk.
1997: Translated into Java as JUnit by Kent Beck and Eric Gamma
Bootstrapped: used JUnit to test when developing JUnit!
NUnit: .NET version using annotations:
TestMethodName() → [Test] MethodName()
Now:
- %UnitTest in Caché
- built in to Visual Studio for .NET
Interview with Kent Beck: http://www.se-radio.net/2010/09/episode-167-the-history-of-junit-and-the-future-of-testing-with-kent-beck/

Test Driven Development (TDD)

Test First

First thing you do is write a test that fails.

It's not a way of testing: It's a way of (thinking about) development.

red/green/refactor

Small steps, incremental cycle

Re-run. Work clean. Keep fast!

Continuous, automated regression testing.

Pros	Cons
Test in language you code in Automated regression tests	Not a replacement for SQA
Helps design complex logic Encourages short, functional (no side-effects) methods of maintainable, reusable, testable code Easier to refactor	Hard to retrofit existing logic Some things are hard to test: UI, dependencies (mocks/DI)
Saves time overall	Takes more time
"Anyone who continues to think that TDD slows you down is living in the stone age...it's like sterile procedure for surgeons." -- "Uncle" Bob Martin*
Keeps you disciplined	Makes you dogmatic
Programmers taking responsibility for quality of work	Programmers taking responsibility for quality of work J

*https://sites.google.com/site/unclebobconsultingllc/home/articles/echoes-from-the-stone-age

Pro Tips

Don't break the build!

Code Coverage: is 100% enough, or too much?

DRY doesnt apply so much. Beck: "every test should tell a story"

Usually don't move to Production

Gamification?

Writing a test

Structure of a test: AAA Pattern

* Arrange (set up)

* Act (run)

* Assert

Test suite/case (class)

Test (method)

http://c2.com/cgi/wiki?ArrangeActAssert

My extensions for Cache unit testing

Adds Run method (no import/export!)

Wildcard

Summary

Color!

Demonstration Time!

Requirements

IsEmpty(string) should return true for empty string, spaces, $c(0).

IsEmptyDOB(id) should return true if pt identified by id has empty DOB. (time permitting)

Dependencies

Extensions [Download]:

Testing.TestCase

Testing.Manager

Steps

Thank you! Questions?

Slides and code:

http://www.marcstober.com/blog/2012/11/13/nemug-presentation-on-test-driven-development/

Contact:

marcstober@gmail.com

@marcstober

Test Driven Development with %UnitTest