Teil 01 - Introduction

Wilhelm-Schickard-Institut - Technische Informatik

Dr. Jürgen Ruf

Introduction

Software Quality In Industry and Practice

Outline

Organization

Motivation

Introduction & Preliminaries

Overview

Organization

This Course

• Applied Computer Science (Praktische Informatik) • Credits: 4 LP (class + exercises) • SWS: 2 + 1 • Exam: oral or written • Exercises: every week, theoretical or hands-on • Lecturers:

- Dr. Jürgen Ruf, Verification Engineer and Team Lead at IBM - Patrick Heckeler - Stefan Huster - Sebastian Burg

• Related Seminar in summer term (associated topics)

Exercises

• Register at CIS: https://cis.informatik.uni-tuebingen.de/sq-ws-1213/ up to 1.11.2012

- Download weekly exercise sheets - News about lecture and exercises

• Weekly exercises sheets

- 20 points per sheet - 50% overall of points to pass - Corrected by tutor

Fotios Hatziioannidis

- Return digitally in CIS system - Groups of 2 students

• Pool-room B203 in Sand 13

- Send student ID-card number to heckeler@informatik.uni-tuebingen.de

Training group

• Weekly training group - Compulsory attendance

• Possible dates

- Monday: 2 pm to 3 pm 3 pm to 4 pm (after 6 pm)

- Wednesday: Whole day possible

- Thursday: 10 am – 11 am 11 am – 12 am

- Friday: 2 pm – open end

Grading

• Course Grading: 20% exercises, 80% exam

• Exercise Grading: 50% of points: Mark 4

• Exam Grading: 50% of points: Mark 4

• Both must be passed at least with mark 4!!!

• Exam date: 7.2.2013 at lecture time

Motivation “”People often say that

motivation doesn’t last. Well, neither does bathing –

that’s why we recommend it daily.” [Zig Ziglar]

Software Yesterday and Today

Yesterday (~30 years ago) Today Hardware dominated the system Software dominates the system Hardware defined the system behavior

Software defines the behavior

SW only in computers SW everywhere, also controlling safety critical systems

"I think there is a world market for maybe five computers“

"640K Ought to be Enough for Anyone”

Safety Critical Systems

• Medical Devices • Automotive (drive-by-wire) • Air and Space Flight (fly-by-wire) • Power Plants • ...

SW dominated Systems

SW in the 21st Century

• More safety critical, real-time software … • Embedded software is ubiquitous … check your

pockets • Enterprise applications means bigger programs,

more users • Paradoxically, free software increases our expectations! • The web offers a new deployment platform

- Very competitive and very available to more users - Web apps are distributed - Web apps must be highly reliable

Industry desperately needs our inventions and expertise!

Dependability Aspects

Dependability

The ability of a system or component to perform its required functions under stated conditions for a specified period of time.

Ability of a System to perform its agreed Function when required, i.e. 7/24 availability, 42 years MTBF

Avoid catastrophic consequences for the environment

Protecting information from unauthorized access, use, disclosure, disruption, modification, perusal, inspection, recording or destruction.

Reliability

Availability

Safety

Security

Definitions: www.wikipedia.com

The First Bugs

“It has been just so in all of my inventions. The first step is an intuition, and comes with a burst, then difficulties arise—this thing gives out and [it is] then that 'Bugs'—as such little faults and difficulties are called—show themselves and months of intense watching, study and labor are requisite. . .” – Thomas Edison

“an analyzing process must equally have been performed in order to furnish the Analytical Engine with the necessary operative data; and that herein may also lie a possible source of error. Granted that the actual mechanism is unerring in its processes, the cards may give it wrong orders. ” – Ada, Countess Lovelace (notes on Babbage’s Analytical Engine)

Hopper’s “bug” (moth stuck in a relay on an early machine)

Costly Software Failures

NIST report, “The Economic Impacts of Inadequate Infrastructure for Software Testing” (2002)

– Inadequate software testing costs the US alone between $22 and $59 billion annually

– Better approaches could cut this amount in half

Huge losses due to web application failures

– Financial services : $6.5 million per hour (just in USA!) – Credit card sales applications : $2.4 million per hour (in USA)

In Dec 2006, amazon.com’s BOGO offer turned into a double discount

2007 : Symantec says that most security vulnerabilities are due to faulty software

World-wide monetary loss due to poor software is staggering

Spectacular Software Failures

Major failures: Ariane 5 explosion, Mars Polar Lander, Intel’s Pentium FDIV bug

Poor testing of safety-critical software can cost lives : THERAC-25 radiation machine: 3 dead

Mars Polar Lander crash site?

THERAC-25 design

Ariane 5: exception-handling bug : forced self destruct on maiden flight (64-bit to 16-bit conversion: about 370 million $ lost)

We need our software to be dependable Testing is one way to assess dependability

NASA’s Mars lander: September 1999, crashed due to a units integration fault

Toyota brakes : Dozens dead, thousands of crashes

Airbus 319 Safety Critical Software Control

Loss of autopilot

Loss of both the commander’s and the co-pilot’s primary flight and navigation displays !

Loss of most flight deck lighting and intercom

Northeast Blackout of 2003

Affected 10 million people in Ontario,

Canada

Affected 40 million people in 8 US

states

Financial losses of $6 Billion USD

508 generating units and 256

power plants shut down

The alarm system in the energy management system failed due to a software error and operators were not informed of the power overload in the system

What Does This Mean?

Software Quality is getting more and more important

„Do we have enough confidence in computer systems to commit to them what is most valuable for us, our

money and our lives? “ (J.C. Laprie)

Introduction and Preliminaries

Software Lifecycle

Con-cept

Imple-men-tation

Archi-tecture

Deploy

Re-quire-ments

Test Design

Sup-port/

Maintenance

SW Quality in the SW Lifecycle

Phase Participants Aspects Methods/ Outcome

Marketing, PM, Management

Feasibility, cost, risk Cost-benefit-Analysis, Risk-Management plan

PM, clients Client’s needs Functional requirements document, use-cases

Architect, developer, tester

Dependability, maintain-ability, testability, …

Architecture document

Architect, developer, QA

Transform requests into system design

Design documentation and development plan

Developer, QA Implement design in SW Software + SW documentation

Developer, QA Design and execute tests based on requests

Various validation and verification methods, reviews

Developer, architects, sales

Manufacturing, distribution, installation

Developer, sales customer support

Ensure systems dependability in operation

Post implementation and in-process reviews

Concept

Implemen-tation

Architecture

Deploy

Requirements

Design

Support/ Maintenance

SW Quality Needs Structured Processes SW Quality is not coincident or luck, it is a matter of structured processes, good tools and hard work! • Project management processes and plans for

- Requirements-, communication-, cost-, risk-, change-management - Project tracking

• Software development - Software development process (waterfall, V-model, agile, …)

• Software implementation - Coding guidelines - Version control - Documentation

• Software Validation/Verification - Bug tracking - Static checks and reviews - Test plan - SW test techniques - Test automation

Content of Lecture 10

SW Quality Needs Structured Processes SW Quality is not coincident or luck, it is a matter of structured processes, good tools and hard work! • Project management processes and plans for

• Software development - Software development process (waterfall, V-model, agile, …)

• Software Validation/Verification - Bug tracking - Static checks and reviews - Test plan - SW test techniques - Test automation

SW Development: Waterfall

Imple-men-tation

Archi-tecture

Deploy

Re-quire-ments

Design

Sup-port/

Maintenance

SW Development: V-Model

Imple-men-tation

Archi-tecture

Design

Re-quire-ments

Use Cases

Test Cases

ModulTest

Inte-gration

Sys-tem Test

Acceptance Test

Sprint

SW Development: Agile process

Archi-tecture

Re-quire-ments

Product backlog

Sprint backlog

Inte-gration

2-6 weeks

Design

ModulTest Imple-

men-tation 24 hours

Daily SCRUM meeting

Potentially shippable product

increment

Sys-tem Test

Acceptance Test

SW Quality Needs Structured Processes Software quality is not coincidence or luck, Software quality is matter of structured processes, good tools and hard work! • Project management processes and plans for

• Software development - SW development process (waterfall, V-model, agile, …)

• Software Validation/Verification - Bug tracking - Static checks - Reviews - Test plan - SW test techniques - Test automation

Coding Guidelines

• Unification of different coding styles - Quicker understanding of “foreign” code - Increases maintainability

• Error reduction - Avoiding error prone constructs (dynamic memory allocation,

pointer arrithmetic, …) • Mandatory in safety critical applications

- i.e. MISRA/MISRA C++ in automotive applications - http://www.ristancase.com/html/dac/manual/3.12.02%20MISRA-C%202004%20Rules.html

• Naming of identifiers, indentation, white spaces, declarations (i.e. avoid shadowing), comments, statements (i.e. one statement per line)

Indent Styles (from www.wikipedia.de)

• K&R style (Kernighan & Richie)

• 1TBS

("the one true brace style“) • GNU style

Version Control Scenarios • Scenario 1:

- Multiple developers work on one product at the same time - How do you manage multiple “locally changed” versions and

how do you merge them to one unit?

Version Control: Concurrency

Repository

Commit: Moves changed File back to repository

Check-out: creates a local copy Of the repository

Commit: Leads to up-2-date fail

Update: Merges changes or Leads to a conflict

Commit

Sandbox Sandbox

how do you merge them to one unit? • Scenario 2:

- Version 1 of your product is shipped - You are working on Version 2 - Now a customer finds a severe bug in Version 1 which needs

to be fixed ASAP - How do you manage multiple levels of your product

Version Control: Tagging

1.0 1.0

fileA fileB fileC

tag command

1.2 1.2

Development Branch Shipped Product Branch

Version Control: Branching

2.1 Branch tag Version delivered to customer

2.2 Bugfix for customer

5 Merge branch to head

how do you merge them to one unit? • Scenario 2:

- Version 1 of your product is shipped - You are working on Version 2 - Now a customer finds a severe bug in Version 1 which needs

to be fixed ASAP - How do you manage multiple levels of your product

• Scenario 3: - Your working on a large scale development project. You

believe one of your team members has added malicious code to the project

- How do you monitor what they’ve changed in your 10,000 line, or 100,000 line project?

Version Control: diff, stat, log

• Information about file status • Information about file history • Different versions of files can be compared:

- Two versions (same or different branches) - Version with sandbox

Showing Branches and Tags

Showing Differences of Versions

Bug Tracking/Defect Management

The test team found a bug • How to document and communicate to the development team • How to track the progress of the bug correction • How does management know what bugs are “out there”?

defect database

test engineer

designer

project manager

report statistics

Bug states in Bugzilla

www.bugzilla.org

• Software development and architecture - SW development process (waterfall, V-model, agile, …)

Static Code Analysis

• Software measurement • Coding style analysis or pretty printer • Syntax checking

- What a compiler needs to do anyway • Semantic analysis

- Lint: more strict type checking, detects unused variable, … - Many compilers do lint-like checking g++ -Wall –ansi –pedantic …

• Exploit analysis - Syntactic analysis reports usage of unsecure functions

(e.g. gets, strcpy) - Semantic analysis methods

• Formal software verification (proof, calculus) • Anomaly analysis

More details in lectures 8 & 9

More details in lecture 11

Anomaly Detection in Dataflows

• Static analysis of - Definition (d) of variables, x = 5 - Reference (r) of variables, if ( x>3 ), y = x + 2 - Variable becomes undefined (u), e.g. end of variable scope,

variable is also undefined after its declaration

Program code inOutMin inOutMax help Void MinMax ( int& inOutMin, d int& inOutMax ) d { int help; u if ( inOutMin > inOutMax ) { r r inOutMax = help; d r inOutMax = inOutMin; r d help = inOutMin; r d } } u

ur-Anomaly

dd-Anomaly

du-Anomaly

Reviews

Walkthrough Review Inspection

What? Ask your peer to have a look at your code

Where? In front of code owner’s monitor

Formal? No

Spontaneous? Yes

Moderated? No

Reviews

Like a Walkthrough but with checklists (often more attendees)

Workplace, or team room, also as offline review possible

Formal? No Yes

Spontaneous? Yes Yes

Moderated? No No

Reviews

Like a Walkthrough but with checklists (often more attendees)

Moderated review process Using project management techniques like phases, documents and clearly defined roles

Workplace, or team room, also as offline review possible

Team room

Formal? No Yes Yes

Spontaneous? Yes Yes no

Moderated? No No Yes

Test Plans

• Why writing test plans? - Documentation of what needs to be done - Good starting point for new team members - Reference for testers - Documentation of what has been done

(good to know in case of field bugs, also to improve testing for next iteration)

• It’s the contents that are important, not the structure - Good testing is more important than proper documentation - However – documentation of testing can be very helpful

• Most organizations have a list of topics, outlines, or templates

Types of Test Plans

• Mission plan – tells “why” - Usually one mission plan per organization or group - Least detailed type of test plan

• Strategic plan – tells “what” and “when”

- Usually one per organization, or perhaps for each type of project - General requirements for coverage criteria to use

• Tactical plan – tells “how” and “who”

- One per product - More detailed - Living document, containing test requirements, tools, results and

issues such as integration order

Test Plan Contents – System Testing

• Purpose • Target audience and application • Deliverables • Information included

- Introduction - Test items - Features tested - Features not tested - Test criteria - Pass / fail standards - Criteria for starting testing - Criteria for suspending testing - Requirements for testing restart

– Hardware and software requirements

– Responsibilities for severity ratings

– Staffing & training needs – Test schedules – Risks and contingencies – Approvals

Test Plan Contents – Tactical Testing

• Purpose • Outline • Test-plan ID • Introduction • Test reference items • Features that will be tested • Features that will not be tested • Approach to testing (criteria) • Criteria for pass / fail • Criteria for suspending testing • Criteria for restarting testing • Test deliverables

• Testing tasks • Environmental needs • Responsibilities • Staffing & training needs • Schedule • Risks and contingencies • Approvals

Content of lectures 2-7

Software Testing Terms

Like any field, software testing comes with a large number of specialized terms that have particular meanings in this context

• Some of the following terms are standardized, some are used

consistently throughout the literature and the industry, but some vary by author, topic, or test organization

• The definitions here are intended to be the most commonly used

Validation & Verification (IEEE)

• Validation : The process of evaluating software at the end of software development to ensure compliance with intended usage

• Verification : The process of determining whether the products of a given phase of the software development process fulfill the requirements established during the previous phase

Test Engineer & Test Managers

• Test Engineer : An IT professional who is in charge of one or more technical test activities

- designing test inputs - producing test values - running test scripts - analyzing results - reporting results to developers and managers

• Test Manager : In charge of one or more test engineers

- sets test policies and processes - interacts with other managers on the project - otherwise helps the engineers do their work

Static and Dynamic Testing

• Static Testing: Testing without executing the program - This include software inspections and some forms of analyses - Very effective at finding certain kinds of problems – especially

“potential” faults, that is, problems that could lead to faults when the program is modified

• Dynamic Testing: Testing by executing the program with

real inputs

Software Faults, Errors & Failures

• Software Fault : A static defect in the program code of the software - Example: infinite program loop

• Software Failure : External, incorrect behavior with respect to the

requirements or other description of the expected behavior. Failures are observed when the software is executed

• Software Error : An incorrect internal state that is the manifestation of some fault or: Human interaction which produces an incorrect result

• Testing : Finding inputs that cause the software to fail

• Debugging : The process of finding a fault given a failure

Fault & Failure Model

Three conditions necessary for a failure to be observed

1. Reachability : The location or locations in the program that contain the fault must be reached

2. Infection : The state of the program must be incorrect

3. Propagation : The infected state must propagate to cause some output of the program to be incorrect

Test Case

• Test Case Values : The values that directly satisfy one test requirement

• Expected Results : The result that will be produced when executing the test if the program satisfies it intended behavior

Observability and Controllability

• Software Observability : How easy it is to observe the behavior of a program in terms of its outputs, effects on the environment and other hardware and software components

- Software that affects hardware devices, databases, or remote files have low observability

• Software Controllability : How easy it is to provide a program with

the needed inputs, in terms of values, operations, and behaviors - Easy to control software with inputs from keyboards - Inputs from hardware sensors or distributed software is harder - Data abstraction reduces controllability and observability

Course Overview

Overview

Software Quality Introduction

Functional Testing (ISP & SBT)

Graphs

Software Testing Verification

Formal I

Formal II

Conclusion

General Testing

Techniques (Unit Test,

Regression)

2. Lecture 3. Lecture 4., 5., 6. Lecture

7. Lecture

8., 9. Lecture

Measuring

Processes & Measuring

Processes& Norms

10., 11. Lecture

Source

Spec & Design

Bibliography

• Peter Ligesmeyer, Software-Qualität - Chapter 1 (Introduction) - Chapter 8.5 (Static Code Analysis)

• Dirk W. Hoffmann, Software-Qualität - Chapters 1-2 (Introduction) - Chapter 5 (Static code analysis) - Chapter 7 (Software Life Cycle) - Chapter 8 (Software Infrastructure)

• P. Ammann & J. Offutt, Introduction to Software Testing - Chapter 1 (Introduction) - Chapter 6.4 (Test Plans)

Teil 01 - Introduction

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