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Agile Developers Go Testing Part II. Darcy Casselman @ flying_squirrel Alexei Zheglov @az1. November 2010. What are we talking about today?. A lot of things… They may seem disconnected, but they all: improve software quality involve testing done by developers
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Agile Developers Go TestingPart II Darcy Casselman @flying_squirrel Alexei Zheglov @az1 November 2010
What are we talking about today? • A lot of things… • They may seem disconnected, but they all: • improve software quality • involve testing • done by developers • None of them can do the job alone • We cannot: • Talk about all of them • Give them equal time
Unit Testing • We showed you a very simple unit test example earlier • We’ll show you a more difficult example later • Let’s step back first
Focus on Quality quotes "...in 2000, during the dot-com bubble, ... software quality for North American teams... ranged from 6 defects per function point to less than 3 per 100 function point, a range of 200 to 1. The midpoint is approximately 1 defect per 0.6 to 1.0 function points. This implies that it is common for teams to spend more than 90 percent of their effort fixing defects.” http://www.amazon.com/Kanban-David-J-Anderson/dp/0984521402/ http://www.amazon.com/Software-Assessments-Benchmarks-Best-Practices/dp/0201485427/
Logical Connection? “The midpoint is approximately 1 defect per 0.6 to 1.0 function points. This implies that it is common for teams to spend more than 90 percent of their effort fixing defects.” How does he know what they are spending their time on?
= Capacity Allocation To Fixing Defects Defect Injection Rate
Bugs, Features http://www.flickr.com/photos/dratz/1045336659/
Another View • Root-cause analysis of established practices • E.g. unit testing • Five-whys applied to the solution, not the problem • The link between the third and fourth whys? Source: Karl Scotland http://availagility.co.uk/2010/10/04/a-root-cause-analysis-of-agile-practices/
Compare Two Teams Team A Team B 10 features 8 bugs • Just finished 40 “features” (units of work) • Introduced 10 “bugs” (units of rework)
Team A Progression • Terms beyond the first three are negligible • Most defects eliminated in the next 2 releases • The 2nd maintenance release scope is very small • Illusion that any team can do it • Time spent fixing defects: 25%
Team B Progression • The sum of the first 3 terms: only 24.4 (less than half of the total!) • The sum of the first 10: approx. 45 • Time spent fixing defects: 80%
We want to be more like Team A (or better) and certainly not like Team B
Testing • Is what we are talking about today • Leaving out other technical practices • Remembering that testing itself does not provide quality
Test Matrix Sources: Robert C. Martin, Rob Diana http://regulargeek.com/2009/06/12/how-much-testing-is-enough/
Test Matrix Sources: Robert C. Martin, Rob Diana http://regulargeek.com/2009/06/12/how-much-testing-is-enough/
Test Matrix Sources: Robert C. Martin, Rob Diana http://regulargeek.com/2009/06/12/how-much-testing-is-enough/
Consider This Test Script • A new customer registers • The customer places three books in the shopping cart • The customer goes to check-out • The customer fills in their delivery address (province: Ontario) • The system offers free delivery to the customer Source: GojkoAdzic. Bridging the Communication Gap, pp. 78-79 http://www.amazon.com/gp/product/0955683610
Compare the Test Script to This The system offers free delivery to Ontario customers when they place their first order and their order contains at least three books
How To Do It • Collaborate: • developers • business analysts • testers • product owner • Which tool to use is not as important • Don’t look up terminology in Wikipedia
Books http://www.amazon.com/gp/product/0955683610 http://manning.com/adzic/
Unit-TestingWhen System Under Test (SUT)Has Dependencies Break the dependencies
What If We Don’t? • Configuration • Database data • Remote services • Permissions • Time to run • Infrequent errors • Dependencies in development
Can You Run Unit Tests Like This? http://www.flickr.com/photos/theredproject/2878006012/
Code Example Caller StudentRepository GradingEngine NotificationService
Code Example Unit Test Stub System Under Test Mock
Source http://www.osherove.com/blog/2010/9/10/2010-poll-which-isolation-framework-do-you-use-in-net.htmlSeptember 2010
Two Camps Design for Testability: Moq, RhinoMocks, etc. Mock Anything, e.g. Typemock Isolator, JustMock Rely on Profiler API Can intercept anything and run something else instead Can fake statics, sealed classes, etc. Don’t force design for testability • Dynamically fake objects implementing interfaces/base classes in their own way • Require software under test to be designed to be testable • Programmers to follow SOLID principles (esp. Dependency Inversion Principle)
Popular Frameworks (Java) • “Conventional”: • Mockitohttp://code.google.com/p/mockito/ • EasyMockhttp://easymock.org/ • JMockhttp://www.jmock.org/ • Alternative: • JMockithttp://code.google.com/p/jmockit/
Roy Osherove • The Chief Architect at TypeMock • Wrote: “A customer switches to Moq – and I’m happy” • And: “This is pure awesome. This is why I come to work every day.” • How is it possible? • Read it: http://www.osherove.com/blog/2010/9/29/a-customer-switches-to-moq-and-im-happy.html
Back to Our Code Example • Grading engine operates on Student and Grade • But Student has a Department • And Grade has a Course and Course has a Semester • We start mocking • Soon, we have a lot of mocks
“Every time a mock returns another mock a fairy dies” • Who said it? • Not the guy whose tweet comes up first in Google search results • I am not 100% sure • What the heck does it mean anyway?
“Every time a mock returns another mock a fairy dies” • Who said it? • Not the guy whose tweet comes up first in Google search results • I am not 100% sure • What the heck does it mean anyway? • We don’t have time for it in this presentation
http://www.amazon.com/Growing-Object-Oriented-Software-Guided-Tests/dp/0321503627/http://www.amazon.com/Growing-Object-Oriented-Software-Guided-Tests/dp/0321503627/
Creating Objects • Constructor injection (as in our code example) • Factory • What if dependencies have dependencies? • What if dependencies of dependencies have dependencies?
Pretty Soon, Things Begin To Look Like This (and this is a simple example) (different box color = different life span) Source: http://ayende.com/Blog/archive/2010/01/22/rejecting-dependency-injection-inversion.aspx
These Tools Can Help • StructureMap • Castle Windsor • Unity • NInject • autofac