Ten Simple Rules for Writing Great Testcases

#DevoxxUS @spoole167 @stuartmarks

TEN SIMPLE RULES FOR WRITING GREAT TESTCASES


Steve Poole : IBM

JVM Developer

DevOps practitioner

Developer Advocate

Stuart Marks : Oracle

Principal MTS

Java / OpenJDK Core Libraries


“I get paid for code that works, not for tests”

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1. Think before you act2. Make your tests understandable3. Keep your tests “small and simple”4. Test one thing only5. Fast tests only6. Absolute repeatability7. Independent tests only8. Provide diagnostic data on failure 9. No hard-coding of your environment10.No extraneous output


1. Think before you act

What are you testing?

Why are you testing?

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2. Make your tests understandable

Comments

Expected behaviour

Aid debug

Diagnostics

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3. Keep your tests “small and simple”

Separate test logic / setup

Much easier to debug

Use setup / teardown

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4. Test one thing only

One scenario per test

Enables fast debug

Obvious why test failed

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5. Fast tests only

Run unit tests often as possible

Maintain quality bar

Quick results

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6. Absolute repeatability

Non-deterministictests are a headache

Fix intermittent tests immediately

No value, waste of resource

Must trust all tests

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7. Independent tests only

Must run in any order

Run subset, faster results

No dependencies

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8. Provide diagnostic data on failure

Use message in asserts

Make it simple to debug

Reference input dataRecord test environment info ht

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9. No hard-coding of your environment

No ports, IP addresses,data files, databases

Use config files, systemproperties or mock objects

Portable tests

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10. No extraneous output

A passing test is a silent test

Too much output = confusion

Use option, config file toturn on debug, save output

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Pirate rules

Guidelines only

Some may seen obvious.

Some may seem pedantic

Until you inherit a testsuite…

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Ten Simple Rules for Writing Great Testcases