Put fastback in fast feedbackLars ThorupZeaLake Software Consulting

October, 2013

Who is Lars Thorup?

● Software developer/architect● C#, JavaScript and C++● Test Driven Development

● Coach● Agile engineering practices● Assessing software projects and

companies

● @larsthorup

Fast feedback is important● Cost of change

● Defects found quickly● ...are cheap to fix

● Lower risk● Systems delivered frequently ● ...are easy to adapt to evolving

requirements

● Fast feedback will make you more productive

How are you doing?

Unit test run time seconds few minutes > 10 minutes

Unit test coverage <25% <50% >50%

Integration test run time minutes > 30 minutes hours

Commits per dev per day 10 1 <1

Releases per week 50 1 <1

Visible metrics of this trend lines status no

Real life stories● Slow feedback

● Large insurance system provider

● Nightly builds, Selenium tests only

● 4 hours, usually some failures

● Weekly commits

● Slow feedback● Large online store● Huge number of Selenium

tests● 12 hours, usually >25%

failures

● Fast feedback● Large interactive meetings● Hourly commits● 75% unit test coverage● <5 minute to build, test and

release

● Fast feedback● Same large online store● Daily commits● 75% unit test coverage● <2 minutes to test● 1/10th QA issues

Feedback goals● Slow feedback, if you:

● Get <10% of your code coverage through unit tests

● Manual or nightly builds● Weekly commits● Merge feature branches on

a monthly basis

● Fast feedback: if you● Get >75% of your code

coverage through unit tests● Release on every commit● Commit many times every

day● Avoid branching in the

version control system● ...instead do branch by

abstraction in the code● http://martinfowler.com/bliki/

BranchByAbstraction.html

Show - don't tell● C# unit testing

● nant unittest / TestDriven.NET

● JavaScript unit testing● grunt test:unit / all.test.html

● TeamCity● Fast build, artifacts● Code coverage

Techniques, tools and metrics

Elephant carpaccio● How do you build an elephant - one slice at a time

● Smaller slices give faster feedback

Start Release date

Time

Mocks and stubs● When testing an object X, that depends on an object Y

● replace the real Y with a fake Y

Notifier

EmailSvc

IEmailSvc

EmailSvcStub

NotifierTest

Test-Driven Development

Failingtest

Succeedingtest

Gooddesign Refactor

Test

IdeaThink, talk

● Every TDD microstep gives you fast feedback

Enforce "fast"● Break the build when it's not fast

Tools● JavaScript

● Jasmine● QUnit● SinonJS● GruntJS● Karma● Istanbul

● .NET● NUnit● NSubstitute● NAnt● NCover

● Java● JUnit● Mockito● Cobertura

● C++● Google Test● Google Mock● Mockito++

● Continuous Integration● Jenkins● TeamCity

Metric - commit frequency

Metric - unit test run time

Metric - unit test coverage

Metric - release frequency

It's not hard - now go do it!● This is hard

● SQL query efficiency● Cache invalidation● Scalability● Pixel perfect rendering● Cross-browser compatibility● Indexing strategies● Security● Real time media streaming● 60fps gaming with HTML5

● ... and robust Selenium tests!

● This is not hard● Unit testing● Dependency injection● Automated build and test● Continuous Integration

● Fast feedback will make you more productive

● ... and more happy