Ten things you should know when writing good unit test cases

© 2013 IBM Corporation

Paul Thwaite IBM, Stuart Marks Oracle.

BOF 4255

Ten Things You Should Know When Writing Good Unit Test Cases in Java

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2


Who are we?

Paul Thwaite– QA Engineer, IBM

Stuart Marks– Principal Member of Technical Staff, Oracle


1. Think before you act

2. Make your tests understandable

3. Keep your tests “small and simple”

4. Test one thing only

5. Fast tests only

6. Absolute repeatability

7. Independent tests only

8. Provide diagnostic data on failure

9. No hard-coding of your environment

10. No extraneous output






5. Fast tests only






What are you testing?

Why are you testing?

Plan






5. Fast tests only






Comments

Expected behaviour

Aid debug

Diagnostics






5. Fast tests only






Separate test logic / setup

Much easier to debug

Use setup / teardown






5. Fast tests only






One scenario per test

Enables fast debug

Obvious why test failed






5. Fast tests only






Run unit tests often as possible

Maintain quality bar

Quick results






5. Fast tests only






Non-deterministic testsare a headache

Fix intermittent tests immediately

No value, waste of resource

Must trust all tests






5. Fast tests only






Must run in any order

Run subset, faster results

No dependencies






5. Fast tests only






Use message in asserts

Make it simple to debug

Reference input data

Record test environment info






5. Fast tests only






No ports, IP addresses,data files, databases

Use config files, systemproperties or mock objects

Portable tests






5. Fast tests only






A passing test is a silent test

Too much output = confusion

Use option, config file toturn on debug, save output


Over to you

What are your experiences with unit testing ideals vs. real world?

What testing problems and pathologies have you encountered?

What are the root causes of your testing problems?

What is the cost of test maintenance?

© 2013 IBM Corporation16

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Ten things you should know when writing good unit test cases

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