selected topics of software technology 3 code smells topics of software technology 3 2 code smells...

Selected Topics of Software Technology 3 Code Smells 1

S C I E N C E P A S S I O N T E C H N O L O G Y

www.tugraz.at

Selected Topics of Software Technology 3 Code Smells

Birgit Hofer Institute for Software Technology

Selected Topics of Software Technology 3 Code Smells 2

Outline

Motivation − Video about Spreadsheet disasters

Code Smells in Software − What smells? − Tools

Code Smells in Spreadsheets − What smells? − Tools

Selected Topics of Software Technology 3 Code Smells 3

Outline

Motivation − Video about Spreadsheet disasters

Code Smells in Software − What smells? − Tools

Code Smells in Spreadsheets − What smells? − Tools

Selected Topics of Software Technology 3 Code Smells 4

Spreadsheets The Ununderstood Dark Matter of IT

Felienne Hermans, Delfth University of Technology

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Number of spreadsheets

Who Estimated Real Investment Bank 10 000 2.5 million

Birgit Hofer 5 000 • xls: 11 034 (76 regular / 10 958 benchmarks)

• xlsx: 2 116 (119 regular / 1 997 benchmarks)

• online: 23

Peter 60 • PC: 136 • Laptop: 16

Thomas ? • xls: 140 • xlsx: 65

Petra 5 000 • xls: 5 547 • xlsx: 836 • online: 1

Christoph ? • xls: 10 • online: 10

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Outline

Motivation − Video about Spreadsheet disasters

Code Smells in Software − What smells? − Tools

Code Smells in Spreadsheets − What smells? − Tools

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What are Code Smells?

Any symptom in the source code of a program that possibly indicates a deeper problem. Not bugs, but they increase the risk

of introducing bugs. Indicate the need of refactoring.

Static Code Analysis

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Code Smells in Software Code Smells within Classes − Coding standard − Long methods − Long parameter list − Duplicated code − Large classes − Dead code

Code Smells between Classes − Inappropriate Intimacy − Data clumps − Indecent Exposure − Feature Envy − Message Chains

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Tools for Detecting Code Smells

Java − Checkstyle − FindBugs − PMD

C/C++ − Lint

.Net − CodeIt.Right

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Outline

Motivation − Video about Spreadsheet disasters

Code Smells in Software − What smells? − Tools

Code Smells in Spreadsheets − What smells? − Tools

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Relevant Literature Hermans, Pinzger and van Deursen:

“Detecting Code Smells in Spreadsheet Formulas”, Int. Conference on Software Maintenance (ICSM) 2012.

Hermans, Pinzger and van Deursen: “Detecting and visualizing inter-worksheet smells in spreadsheets”, Int. Conference on Software Engineering (ICSE) 2012.

Kulesz and Ostberg: “Practical Challenges with Spreadsheet Auditing Tools”, European Spreadsheet Risks Interest Group Conf. (EuSpRIG), 2013.

Cunha, Fernandes, Ribeiro and Saraiva: “Towards a Catalog of Spreadsheet Smells”, Int. Conf. on Computational Science and Its Applications (ICCSA), 2012.

Cunha, Fernandes, Martins, Mendes and Saraiva: “SmellSheet detective: A tool for detecting bad smells in spreadsheets”, Symp. on Visual Languages and Human-Centric Computing (VL/HCC) 2012

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Formula Smells

Multiple Operations

Multiple References

Conditional Complexity

Long Calculation Chains

Duplicated Formulas

Source: Hermans, Pinzger and van Deursen: “Detecting Code Smells in Spreadsheet Formulas”, Int. Conference on Software Maintenance (ICSM) 2012.

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Inter-worksheet Smells

Inappropriate Intimacy

Feature Envy

Middle Man

Shotgun Surgery

Source: Hermans, Pinzger and van Deursen: “Detecting and visualizing inter-worksheet smells in spreadsheets”, Int. Conference on Software Engineering (ICSE) 2012.

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Other Code Smell for Spreadsheets Statistical smells o Standard deviation

Type smells o Empty cell o Pattern finder

Content smell o String distance o Reference to empty cells

Functional dependencies based smells o Quasi-Functional Dependencies (QFD)

Source: Cunha, Fernandes, Ribeiro and Saraiva: “Towards a Catalog of Spreadsheet Smells”, Int. Conf. on Computational Science and Its Applications (ICCSA), 2012.

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Code Smells Examples

Standard deviation Pattern finder

Empty cell QFD

String distance

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Standard Deviation – How to identify data outliers?

Conditional formatting

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Empty Cell Smell – How to identify?

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Empty Cell Smell – How to identify?

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Empty Cell Smell – How to identify?

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Empty Cell Smell – How to identify?

Empty cell

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Tools for Detecting Code Smells

SIF (Spreadsheet Inspection Framework) − https://github.com/kuleszdl/Spreadsheet-Inspection-Framework

SmellSheet Detective and FaultySheet Detective − http://ssaapp.di.uminho.pt/twiki/bin/view/Main/Software

Breviz − Tool developed at TU Delfth, download?

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Some remarks

Determining thresholds could be difficult

Handling of false positives Time-consuming and boring

Configuration Adjustable

Challenge:

How to convince users of “higher quality” related issues like maintenance?

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Some remarks – Output representation

Flat list of findings Links missing (navigation) Lists ordered after severity or grouped by type

Separate file Links missing Cell coloring and comments added Take care with spreadsheets that rely on conditional formatting Not too many colors, use intuitive colors

Critical smell Non-critical smell

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Outline

Motivation − Video about Spreadsheet disasters

Code Smells in Software − What smells? − Tools

Code Smells in Spreadsheets − What smells? − Tools