Tests Why Testing is Important Damien Cassou, Stphane Ducasse and - - PowerPoint PPT Presentation

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Sep 26, 2022 909 likes •1.16k views

Tests Why Testing is Important Damien Cassou, Stphane Ducasse and Luc Fabresse WXSYY http://www.pharo.org Goal why tests are important? what are their advantages? what are the techniques to write good tests? WXSYY 2 / 24 Pros

SLIDE 1

Tests

Why Testing is Important

Damien Cassou, Stéphane Ducasse and Luc Fabresse

WXSYY

http://www.pharo.org

SLIDE 2

Goal

why tests are important? what are their advantages? what are the techniques to write good tests? WXSYY 2 / 24

SLIDE 3

Pros

Finding problems Understanding code Increase trust Collateral pros WXSYY 3 / 24

SLIDE 4

Finding Problems: Pros

find bugs when they appear improve customer trust reproduce complex scenari check contracts of super types guarantee old bugs won’t come back isolate the problem WXSYY 4 / 24

SLIDE 5

Finding Problems: Characteristics of a Good Test Suite

check extreme cases (e.g., null, 0 and empty) check complex cases (e.g., exceptions, network pbs) 1 test for each bug (at least) good coverage check abstractions check units independently WXSYY 5 / 24

SLIDE 6

Understanding Code

convert | s | s := '#000000' copy. s at: 2 put: (Character digitValue: ((rgb bitShif: −6 − RedShif) bitAnd: 15)). s at: 3 put: (Character digitValue: ((rgb bitShif: −2 − RedShif) bitAnd: 15)). s at: 4 put: (Character digitValue: ((rgb bitShif: −6 − GreenShif) bitAnd: 15)). s at: 5 put: (Character digitValue: ((rgb bitShif: −2 − GreenShif) bitAnd: 15)). s at: 6 put: (Character digitValue: ((rgb bitShif: −6 − BlueShif) bitAnd: 15)). s at: 7 put: (Character digitValue: ((rgb bitShif: −2 − BlueShif) bitAnd: 15)). ^ s

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SLIDE 7

Understanding Code

testConvert self assert: Color white convert = '#FFFFFF'. self assert: Color red convert = '#FF0000'. self assert: Color black convert = '#000000'

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SLIDE 8

Understanding Code

testConvert2 | table aColorString | table := #('0' '1' '2' '3' '4' '5' '6' '7' '8' '9' 'A' 'B' 'C' 'D' 'E' 'F'). table do: [ :each | aColorString := '#', each, each, '0000'. self assert: ((Color fromString: aColorString) convert sameAs: aColorString)]. table do: [ :each | aColorString := '#', '00', each, each, '00'. self assert: ((Color fromString: aColorString) convert sameAs: aColorString)]. table do: [ :each | aColorString := '#', '0000', each, each. self assert: ((Color fromString: aColorString) convert sameAs: aColorString)].

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SLIDE 9

Understanding Code

testBitShif self assert: (2r11 bitShif: 2) equals: 2r1100. self assert: (2r1011 bitShif: −2) equals: 2r10. testShifOneLefThenRight "Shif 1 bit lef then right and test for 1" 1 to: 100 do: [:i | self assert: ((1 bitShif: i) bitShif: i negated) = 1].

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SLIDE 10

Understanding Code: Pros

give simple and reproducible examples explain an API give up-to-date documentation check conformity of new code

ffer a first client to new code

force a modular design WXSYY 10 / 24

SLIDE 11

Understanding Code: Characteristics of a Good Test Suite

deterministic automatic self-explained simple unit WXSYY 11 / 24

SLIDE 12

Increasing Trust: Pros

accelerate bug detection accelerate new code checking ease refactorings prevent regressions WXSYY 12 / 24

SLIDE 13

Increasing Trust: Characteristics of a Good Test Suite

change less frequently than the rest good code coverage deterministic WXSYY 13 / 24

SLIDE 14

Collateral Pros

improve feeling of customers who care allow for automatic bug fixing improve type inference provide examples to variable values WXSYY 14 / 24

SLIDE 15

Testing Abstractions

How do you test contracts of abstract types?

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SLIDE 16

Testing Abstractions

How do you test that one and only one state is active at any time?

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SLIDE 17

Testing Abstractions

testOnlyOneValidStateAtEachMoment | action | action := self createAction. self assert: action isReady. self deny: action isInProgress. self deny: action isFinished. [ action isFinished ] whileFalse: [ action doStep. self deny: action isReady. self assert: action isFinished = action isInProgress not ]. self deny: action isReady. self deny: action isInProgress. self assert: action isFinished

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SLIDE 18

Testing Abstractions

parallel hierarchies test must be in the highest abstraction factory method WXSYY 18 / 24

SLIDE 19

Mocking

How do you test that a questionnaire only accepts compatible answers from the user?

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SLIDE 20

Mocking

How do you test that a questionnaire only accepts compatible answers from the user?

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Mocking

readAnswerAsLongAsItIsNotCompatible | nbRejectsBeforeAccept question ui | nbRejectsBeforeAccept := 3. question := MockQuestion new nbRejects: nbRejectsBeforeAccept. ui := MockQuestionnaireUI new. self assert: ui nbReadAnswers equals: 0. self assert: question nbAcceptAnswerCalls equals: 0. questionnaire runQuestion: question on: ui. self assert: ui nbReadAnswers equals: nbRejectsBeforeAccept + 1. self assert: question nbAcceptAnswerCalls equals: nbRejectsBeforeAccept + 1.

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SLIDE 22

Mocking

mocks are reusable across tests mocks can be generated with mocking frameworks WXSYY 22 / 24

SLIDE 23

Different Testing Levels

http://martinfowler.com/bliki/TestPyramid.html

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SLIDE 24

A course by and in collaboration with

Inria 2016 Except where otherwise noted, this work is licensed under CC BY-NC-ND 3.0 France https://creativecommons.org/licenses/by-nc-nd/3.0/fr/