Code quailty metrics demystified
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from DevMotion Meetup on 2016-03-14 In our everyday work as developers, we are confronted with various software metrics. What do these numbers mean, how are they calculated? Do these metrics enable us to make better software? In this talk we investigate the use of software metrics in general and also take a detailed look at several frequently used code quality metrics. We will learn about the meaning and usefulness of metrics such as lines of code, cyclomatic complexity, duplication, package entanglement and unit test coverage.
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Code quailty metrics demystified
- 1. Code Quality Metrics Demystified @JeroenResoort @jdriven_nl
- 4. Why use metrics? To measure software quality
- 5. What is software quality?
- 6. Why use metrics? To measure and improve software maintainability attributes: ● Analysability ● Changeability ● Stability ● Testability
- 7. How to collect metrics?
- 8. How to use / collect metrics? IDE CheckStyle SonarQube
- 9. How to collect metrics? docker run -d --name sonarqube -p 9000:9000 -p 9092:9092 sonarqube mvn sonar:sonar
- 10. Volume
- 11. Volume Files / Classes Lines Lines of code LoC per file LoC per method
- 12. Volume public int sum(int a, int b) { return a + b; }
- 13. Volume public int sumToo( int a , int b ) { int result = a + b; return result; }
- 14. Volume public List<Integer> calculate(List<Integer> numbers) { return numbers.stream().map(i -> i * i).filter(i -> i % 2 == 0).collect(Collectors.toList()); }
- 15. Volume public List<Integer> calculateFormatted(List<Integer> numbers) { return numbers.stream(). map(i -> i * i). filter(i -> i % 2 == 0). collect(Collectors.toList()); }
- 16. Volume import java.util.List; import java.util.ArrayList; import java.util.Set; import java.util.HashSet;
- 19. Cyclomatic Complexity McCabe, 1976 Control flow graph Linearly independent paths
- 21. Cyclomatic Complexity The complexity M is defined as M = E − N + 2P, where E = the number of edges of the graph. N = the number of nodes of the graph. P = the number of connected components.
- 22. Cyclomatic Complexity Alternative formula M = E − N + P After connecting exit point to entry point
- 24. Cyclomatic Complexity public int sum(int a, int b) { return a + b; }
- 25. Cyclomatic Complexity public int sum(int[] amounts) { int result = 0; for (int i = 0; i < amounts.length; i++) { result += amounts[i]; } return result; }
- 26. Cyclomatic Complexity public boolean checkWithdrawal(Account account, int amount) { boolean result = false; if (account.getBalance() >= amount) { result = true; } if (account.isLocked()) { result = false; } return result; }
- 27. Cyclomatic Complexity public boolean checkWithdrawal(Account acc, int amount) { if (!acc.isLocked() && acc.getBalance() >= amount) { return true; } return false; }
- 28. Cyclomatic Complexity Complexity per class Complexity per method
- 29. Fan in / Fan out
- 30. Fan in / Fan out Fan in: number of classes referencing you Fan out: number classes you are referencing
- 33. Duplication
- 34. Duplication How to check? Per line vs multiple lines? Exact match or not?
- 36. Unit Test coverage Bad examples
- 37. Unit Test coverage Are your unit tests actually testing the right things? Mutation tests!
- 38. Conclusion A lot of metrics available Understand what they mean Don’t use metrics as KPIs!
- 39. Questions?
- 40. Code Quailty Metrics Demystified @JeroenResoort @jdriven_nl