how to build an effective automated test suite

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How to build anEffective Automated

Test Suite

David Adsit@davidadsit

codeobsession.blogspot.com

Why test?

Why test?

“Code without tests is bad code. It doesn't matter how well written it is; it doesn't matter how pretty or object-oriented or well-encapsulated it is. With tests, we can change the behavior of our code quickly and verifiably.Without them, we really don't know if our code is getting better or worse.”

- Michael Feathers

3 Great Virtues

“We will encourage you to develop the three great virtues of a programmer: laziness, impatience, and hubris.”

- Larry Wall

The Full Test Suite

The Full Test Suite

Unit Tests

Integration Tests

Acceptance Tests

UI Tests

The Full Test Suite

Unit Tests

Integration Tests

Acceptance Tests

UI Tests

The Full Test Suite

Unit Tests

Integration Tests

Acceptance Tests

UI Tests

The Full Test Suite

Unit Tests

Integration Tests

Acceptance Tests

UI Tests

Unit Tests

Strengths▪ Fast - which means you can have a lot of them▪ Focused feedback when code breaks▪ Provide executable documentation for each unit

Weaknesses▪ Do not verify external dependencies▪ Do not verify that units will work properly together▪ Do not verify that the system supports desired features▪ Do not answer questions about the “-ilities” of the system

Integration Tests

Strengths▪ Verify that external dependencies behave as expected▪ Provide early notification of API changes▪ Facilitate changing external system providers▪ Can tell us about the “-ilities” of external dependencies▪ Help ensure clean boundaries with external dependencies

Weaknesses▪ Usually significantly slower than unit tests▪ Test only a very narrow part of the system▪ Do not verify that the system supports desired features

Acceptance Tests

Strengths▪ Help communicate features and requirements with business▪ Verify the existence of features▪ Help drive a clean API for the system▪ Exercise the full system (excluding the UI)

Weaknesses▪ Slower than unit tests▪ Do not answer questions about the “-ilities” of the system

The Double Loop

Layered Architecture

Eric Evans, Domain Driven Design

User Interface Tests

Strengths▪ Verify that the system can be assembled▪ Verify that the user can interact with the system▪ Can answer questions about the “-ilities” of the system

Weaknesses▪ Slower than the pitch drop experiment▪ Unreliable▪ Require significant maintenance when changes occur▪ Cannot provide confidence about system correctness

Questions

&

Demos

Links

Unit & Integration & Acceptance & UI:https://github.com/davidadsit/LegacyCodeRescue

Unit & Acceptance: https://github.com/davidadsit/bddtddfitnesse

Slides: http://www.slideshare.net/davidadsit

Blog Post:http://codeobsession.blogspot.com/2012/03/simpler-tests-what-kind-of-test-are-you.html

Final Questions?

David Adsit@davidadsit

codeobsession.blogspot.com