Chapter 2

Testing: Introduction

Dssouli rachidaCIISE

Concordia Unieversitydssouli@ciise.concordia.ca

Acknowledgements:Dr. Jerry Gao, Dr. Hong, Dr. En-Nouaary and many others

Verification and validationWhat is Software Testing?

- Definitions- Testing Objectives- Who Does Software Testing?

- Software Testing Activities

- Software Testing Scope

- Software Testing Principles

- Software Testing Process

- Software Testing Myths

- Software Testing Limits

- Different Types of Software Testing

- Testing fundamentals

Introduction outline

Techniques for V&V

• Static– Collects information about a software without executing it

• Reviews, walkthroughs, and inspections• Static analysis• Formal verification

• Dynamic– Collects information about a software with executing it

• Testing: finding errors• Debugging: removing errors

Static Analysis

• Control flow analysis and data flow analysis– Extensively used for compiler optimization and software

engineering• Examples

– Unreachable statements– Variables used before initialization– Variables declared but never used– Variables assigned twice but never used between

assignments– Variables used twice with no intervening assignment– Possible array bound violations

Formal Verification

• Given a model of a program and a property, determine whether the model satisfies the property based on mathematics

• Examples– Safety

• If the light for east-west is green, then the light for south-north should be red

– Liveness• If a request occurs, there should be a response

eventually in the future

Several definitions:

“Testing is the process of establishing confidence that a program or system does what it is supposed to.” by Hetzel 1973

“Testing is the process of executing a program or system with the intent of finding errors.” by Myers 1979

“Testing is any activity aimed at evaluating an attribute or capability of a program or system and determining that it meets its required results.” by Hetzel 1983

What is Software Testing

- One of very important software development phases

- A software process based on well-defined software quality control and testing standards, testing methods, strategy, test criteria, and tools.

- Engineers perform all types of software testing activities to perform a software test process.

- The last quality checking point for software on its production line

What is Software Testing

The Major Objectives of Software Testing:

- Uncover as many as errors (or bugs) as possible in a given product.

- Demonstrate a given software product matching its requirement specifications.

- Validate the quality of a software testing using the minimum cost and efforts.

- Generate high quality test cases, perform effective tests, and issue correct and helpful problem reports.

Major goals:

uncover the errors (defects) in the software, including errors in:- requirements from requirement analysis- design documented in design specifications- coding (implementation)- system resources and system environment- hardware problems and their interfaces to software

Testing Objectives

- Test manager- manage and control a software test project - supervise test engineers- define and specify a test plan

- Software Test Engineers and Testers- define test cases, write test specifications, run tests

- Independent Test Group

- Development Engineers- Only perform unit tests and integration tests

- Quality Assurance Group and Engineers- Perform system testing- Define software testing standards and quality control process

Who does Software Testing

Testing

SoftwareApply input Observe output

Validate the observed output

Is the observed output the same as the expected output?

Oracle

Some Limitations of Testing (I)

• To test all possible inputs is impractical or impossible

• To test all possible paths is impractical or impossible

int foo(int x) { y = very-complex-computation(x); write(y);}

int foo(int x) { for (index = 1; index < 10000; index++) write(x);}

Limitations of Testing (II)

• Dijkstra, 1972– Testing can be used to show the presence of bugs, but

never their absence• Goodenough and Gerhart, 1975

– Testing is successful if the program fails• The (modest) goal of testing

– Testing cannot guarantee the correctness of software but can be effectively used to find errors (of certain types)

Economics of Testing (I)

• The characteristic S-curve for error removal

Number of defects found

Time spent testing

Cutoff pointTesting is effective

We need other techniques

Economics of Testing (II)

Number of defects

Less likely =More critical

Progress of testing

Found Not yet found

• Testing tends to intercept errors in order of their probability of occurrence

Economics of Testing (III)

• Verification is insensitive to the probability of occurrence of errors

Number of defects

Less likely =More critical

Progress of verification

Found

Not yet found

Fundamental Questions in Testing

• When can we stop testing?– Test coverage

• What should we test? – Test generation

• Is the observed output correct?– Test oracle

• How well did we do?– Test efficiency

• Who should test your program?– Independent V&V

Software Testing Scope

Software Testing Process

Software Testing Management

ConfigurationManagement

Software Problem Management

Software Testing Methods

Software Test Criteria

Software TestingTools

Software Test Models

Software Testing Strategies

- Test Planing Define a software test plan by specifying:

- a test schedule for a test process and its activities, as well as assignments- test requirements and items- test strategy and supporting tools

- Test Design and Specification- Conduct software design based on well-defined test generation methods.- Specify test cases to achieve a targeted test coverage.

- Test Set up:- Testing Tools and Environment Set-up- Test Suite Set-up

- Test Operation and Execution - Run test cases manually or automatically

Software Testing Activities

- Test Result Analysis and ReportingReport software testing results and conduct test result analysis

- Problem ReportingReport program errors using a systematic solution.

- Test Management and MeasurementManage software testing activities, control testing schedule, measure testing complexity and cost

- Test Automation- Define and develop software test tools- Adopt and use software test tools- Write software test scripts and facility

- Test Configuration Management- Manage and maintain different versions of software test suites, test

environment and tools, and documents for various product versions.

Software Testing Activities

Verification and Validation

Software testing is one element of a broader topic that is often referred to as ===> Verification and Validation (V&V)

Verification --> refers to the set of activities that ensure that software correctly implements a specific function.

Validation -> refers to a different set of activities that ensure that the software that has been built is traceable to customer requirements.

Boehm [BOE81]:

Verification: “Are we building the product right?”Validation: “Are we building the right product?”

The definition of V&V encompasses many of SQA activities, includingformal technical reviews, quality and configuration auditsperformance monitoring, different types of software testingfeasibility study and simulation

•Principle #1: Complete testing is impossible.

•Principle #2: Software testing is not simple activity.•Reasons:

•Quality testing requires testers to understand a system/product completely•Quality testing needs adequate test set, and efficient testing methods•A very tight schedule and lack of test tools.

•Principle #3: Testing is risk-based.

•Principle #4: Testing must be planned.

•Principle #5: Testing requires independence (SQA team).

•Principle #6: Quality software testing depends on:•Good understanding of software products and related domain application•Cost-effective testing methodology, coverage, test methods, and tools.•Good engineers with creativity, and solid software testing experience

Software Testing Principles

- We can test a program completely. In other words, we test a program exhaustively.

- We can find all program errors as long as test engineers do a good job.

- We can test a program by trying all possible inputs and states of a program.

- A good test suite must include a great number of test cases.

- Good test cases always are complicated ones.

- Software test automation can replace test engineers to perform good software testing.

- Software testing is simple and easy. Anyone can do it. No training is needed.

Software Testing Myths

- Due to the testing time limit, it is impossible to achieve total confidence.

- We can never be sure the specifications are 100% correct.

- We can never be certain that a testing system (or tool) is correct.

- No testing tools can cop with every software program.

- Tester engineers never be sure that they completely understand a software product.

- We never have enough resources to perform software testing.

- We can never be certain that we achieve 100% adequate software testing.

Software Testing Limits

Software Testing Process

Unit test

Integrationtest

Validationtest

Systemtest

System engineering

Requirements

Software Design

Code & Implementation

V&V Targets

Unit Test (Component Level Test)What?Unit testing: Individual components are tested independently to

ensure their quality. The focus is to uncover errors in design and implementation, including

Why? - data structure in a component- program logic and program structure in a component- component interface- functions and operations of a component

Who? : developers of the components.

Operations and Functions with I/O

White-boxinterfaceinput

output

Internal logic, data, structure

output

inputinterface

operation

Black-box

Integration TestingWhat?Integration test: A group of dependent components are composed and tested

together to ensure their the quality of their integration unit.Why? The objective is to detect errors in:

- Design and construction of software architecture- Integrated functions or operations at sub-system level- Interfaces and interactions between them- Resource integration and/or environment integration

Who? Either developers and/or test engineers.

Component #1

Operations and Functions with I/O

input

interface

operation

Component #2

Operations and Functions with I/O

output

interface

operation

System Validation Testing

What?System val. test: The entire integrated software that composes the system is tested based on requirements to ensure that we have a right product.Why ?The objective is to detect errors in:

- System input/output - System functions and information data- System interfaces with external parts- User interfaces- System behavior and performance

Who? test engineers in ITG or SQA people.

System

(Operations &Functions

& Behavior)

Userinterface

User External interfaces

System Testing

What?System test: The system software is tested as a whole. It verifies all

elements mesh properly to make sure that all systemfunctions and performance are achieved in the target environment.

Why? The focus areas are:- System functions and performance - System reliability and recoverability (recovery test)- System installation (installation test)- System behavior in the special conditions (stress and load test)- System user operations (acceptance test/alpha test)- Hardware and software integration and collaboration- Integration of external software and the system

Who? Test engineers in ITG or SQA people.

When a system is to be marketed as a software product, a testing process calledbeta testing is often used.

“beta testing”

Test Issues in Real World

Software testing is very expensive.

How to achieve test automation?

When should we stop software testing?

Test criteria, test coverage, adequate testing.

The test is cost function

Types of Testing

Aspect

Accessibility

Level

functional

robustness

performance

reliability

usability

unitintegrationsystemacceptance

whitebox

greybox

blackbox

regression

Levels of Testing

What usersreally need

Requirements

Design

Code

Acceptance testing

System testing

Integration testing

Unit testing

System Testing

• Tests the overall system (the integrated hardware and software) to determine whether the system meets its requirements

• Focuses on the use and interaction of system functionalities rather than details of implementations

• Should be carried out by a group independent of the code developers

• Should be planned with with the same rigor as other phases of the software development

Regression Testing

• Development versus maintenance– Development costs: 1/3– Maintenance costs: 2/3

• Testing in maintenance phase– How can we test modified or newly inserted programs?

• Ignore old test suites and make new ones from the scratch or

• Reuse old test suites and reduce the number of new test suites as many as possible

Accessibility of Testing

• White box testing (structural testing, program-based testing)– Assumes that the program is available

• Derives test cases from the program• Controls and observes the internal structure of the program

• Black box testing (functional testing, specification-based testing)– Assumes that the program is unavailable or testers do not want to look

at the details of the program• Derives test cases from the requirements of the program• Controls and observes the program only through external interfaces

• Grey box testing

Program-Based Testing (I)

• Main steps– Examine the internal structure of a program– Design a set of inputs satisfying a coverage criterion– Apply the inputs to the program and collect the actual

outputs– Compare the actual outputs with the expected outputs

• Limitations– Cannot catch omission errors

• What requirements are missing in the program?– Cannot provide test oracles

• What is the expected output for an input?

Program-Based Testing (II)

ProgramApply input Observe output

Validate the observed output against the expected output

Who will take care of test oracles?

Specification-Based Testing (I)

• Main steps– Examine the structure of the program’s specification– Design a set of inputs from the specification satisfying a coverage

criterion– Apply the inputs to the specification and collect the expected outputs– Apply the inputs to the program and collect the actual outputs– Compare the actual outputs with the expected outputs

• Limitations– Specifications are not usually available

• Many companies still have only code, there is no other document.

Specification-Based Testing (II)

ProgramActual output

Specification

Apply input

Expected output

Validate the observed output against the expected output

Object-Oriented Program Testing

• Unit testing for OO Programs– A class is a set of variables and member functions– 50% of member functions are just 10 lines of code– A class is often a unit of testing in C++ or Java

• Integration testing for OO Programs– Rule of thumb in OO development

• Make a large number of small classes in a bottom-up fashion – There are several relationships between classes

• Association, aggregation, inheritance, concurrency

- User interface errors, such as output errors, incorrect user messages.

- Function errors - Defect hardware

- Incorrect program version- Testing errors

- Requirements errors - Design errors

- Documentation errors - Architecture errors

- Module interface errors - Performance errors

- Error handling - Boundary-related errors

- Logic errors, such as calculation errors

- State-based behavior errors - Communication errors

- Program structure errors, such as control-flow errors

Categories of Software Errors

Like other activities in software engineering phases, it is impossible to have a cost-effective software test process without a very good planing,

The major objective of software test planing:- generate a well-defined software test plan.

What content should be included in a software test plan?

- Testing activities and schedule- Testing tasks and assignments- Selected test strategy and test models- Test methods and criteria- Required test tools and environment- Problem tracking and reporting- Test cost estimation

Other needed items: quality control process and standards

Software Test Planing

Software Test RequirementsBefore starting test design, we must identify our test objectives, focuses, and test items. The major purpose is to help us understand what are the targets of software testing.

This step can be done based on:- Requirements specifications- Inputs from developers- Feedback from customers

Benefits are:- Identify and rank the major focus of software testing- Check the requirements to see if they are correct, completed, and testable- Enhance and update system requirements to make sure they are testable- Support the decision on selecting or defining test strategy

The essentials of testing requirements include:

- Specified testing methods- Required test types am d test coverage criteria- Selected or required test tools- Testing focuses and test items for each type of software testing

An example of performance testing requirements:

“Check the system performance to make sure it meet 99% system reliability requirements”

A typical example for required test items is:

Test item #I: “Test the call waiting feature (REQ #j) during system testing based on the given requirements specifications.”

Software Test Design

Software test design is an important task for software test engineers.

A good test engineer always know how to come out quality test cases and perform effective tests to uncover as many as bugs in a very tight schedule.

What do you need to come out an effective test set ?

- Choose a good test model and an effective testing method- Apply a well-defined test criteria- Generate a cost-effective test set based on the selected test criteria- Write a good test case specification document

What is a good test case?- It must have a high probability to discover a software error- It is designed to aim at a specific test requirement- It is generated by following an effective test method- It must be well documented and easily tracked- It is easy to be performed and simple to spot the expected results- It avoids the redundancy of test cases

Software Test Design

What content should be included in a test case?.

Test Case ID: Test Item: Wrote By: (tester name) Documented Date:Test Type: Test Suite#:Product Name: Release and Version No.:

Test case description:

Operation procedure:

Pre-conditions: Post-conditions:

Inputs data and/or events: Expected output data and/or events:

Required test scripts:

Test execution can be performed:

- using manual approach- using a systematic approach- using a semi-automatic approach

Basis activities in test execution are:

- Select a test case- Set up the pre-conditions for a test case- Set up test data- Run a test case following its procedure - Track the test operations and results- Monitor the post-conditions of a test case & expect the test results- Verify the test results and report the problems if there is any- Record each test execution

Software Test Execution

What do you need to perform test execution?

- a test plan - test design specification with test case specifications- a test suite with documented test cases (optional)- test supporting facility, such as test drivers, test stubs, simulators

What are the outcome of an test execution:

- Text execution record and report- Problem and bug reports- Error logs and

With automatic test execution tools (or test control tools), we can do:- automatic test runner- record and replay

Software Test Execution

Problem Analysis and Report

When do we issue a problem?

Whenever a bug or problem is found, we need to write down a problem report immediately.

What are the content of a problem report?

Problem ID current software name, release no. and version no.

Test type Reported by Reported date Test case ID

Subsystem (or module name) Feature Name (or Subject)

Problem type (REQ, Design, Coding, …) Problem severity (Fatal, Major, Minor, ..)

Problem summary and detailed description

Cause analysis How to reproduce? Attachments

Problem Analysis and Report

How to track, control, and manage issued problems?

- A systematic solution is needed to track and maintain the reported problems in a repository.- Define and implement a problem control and analysis process to control problemtracking, reporting, analysis, fixing and resolutions.

Characteristics of a problem report:

- Simple and understandable - Traceable and numbered

- Reproducible - Non-judgmental

Problem analysis:-Finding the most serious consequences-Finding the simplest and most general conditions-Finding alternative paths to the same problem-Finding related problems

Software Test Review

What is a review?

- A review is a verification activity to assure a correct method has been used to create a software product. - Participants in a review take full responsibility for results.

There are two types of reviews:

- Formal reviews: - use a well-defined review method (or technique)- generate formal review results

- Informal reviews- use a desk checking approach- conduct an informal review- generate information review results

Software Test Review

Products should be reviewed during software testing:

Test Plan Test Design SpecificationTest Procedure SpecificationTest Report Problem Reports

What do reviews accomplish?

- Reviews provide the primary mechanism for reliably evaluating progress.

- Reviews train and educate the participants and have a significant positive effect on staff competence.

- Reviews give early feedback and prevent more serious problems from arising.

- Reviews bring individual capability to light.

Test Management

Test management encompass:- management of a test team- management of a test process- management of test projects

A test manager’s role:

- Play as a leadership role in: - planing projects - setting up a direction -motivating people- build a team- manage engineers

- Play as a controller in: - product evaluation - performance evaluation- changing to a new direction

- Play as a supporter in:- assist and train engineers - train engineers- enforce and control test methods, standards, and criteria- select and develop test tools

Test Management

Test management functions:

- Management - Manage test projects- Manage team members- Manage test processes

- Motivation - Motivate quality work from team members- Simulate for new ideas and creative solutions

- Methodology - Control of setting up test methodology, process, standards.- Control of establishing test criteria

- Mechanization - Control the selection and development of test tools - Mechanism for the configuration management of test suites- Control of setting up an integrated test environment

- Measurement - Measure test cost, complexity and efforts- Measure engineer performance- Measure test effectiveness- Measure product quality

Test Management

Test management encompass:- management of a test team- management of a test process- management of test projects

A test manager’s role:

- Play as a leadership role in: - planing projects - setting up a direction -motivating people- build a team- manage engineers

- Play as a controller in: - product evaluation - performance evaluation- changing to a new direction

- Play as a supporter in:- assist and train engineers - train engineers- enforce and control test methods, standards, and criteria- select and develop test tools

Test Management

Questions for managers who claim to be managing software testing:

Management:Do you plans address testing?Do you know who is responsible?Have you published your testing policy?

Motivation: Do you provide incentive for people do quality work?Do you encourage people to take advantage of training opportunities in testing methods?

Methodology: Are your testing methods proceduralized and are people trained

in their use?Are you aware of new testing techniques and are you working to introduce them?

Test Management

Questions for managers who claim to be managing software testing:

Mechanization: Do you sufficient hardware and equipment to support testing?Have you provided appropriate software testing tools and aids?Do you evaluate automated testing aids on an ongoing basis?

Measurement: Do you track errors, faults, and failures?

Do you know what testing costs?Do you quantitatively measure testing performance?

Test Engineers’ Tasks

What does a test engineer do?

- Ensure that testing is performed- Ensure that testing is documented- Ensure that testing methodology, techniques, standards are established and developed

The basic skills for a qualified test engineer:

Controlled - Organized individual, systematic planing- Good planing on testing

Competent - Technical awareness of testing methods, tools, and criteria

Critical - Inner determination to discover problems

Comprehensive - Total understanding of the given system and specifications- Pay good attention to the details

Considerate - Ability to related to others and resolve conflicts

Basic Test Engineers’ Tasks

The basic tasks of a test engineer include:

- Prepare testing plans and organize testing activities

- Design test cases and document them using well-defined test methods

- Develop test procedures and test data

- Write problem reports and text execution records

- Use testing tools and aids

- Review test designs, results and problems

- Test maintenance changes

- Oversee acceptance tests

Test Automation and Tools

What is software test automation?

Software test automation refers to a process and activities that reduce manual testing activities and efforts in a software development lifecycle.

Why software test automation?

- Reduce software testing time, cost, and efforts- Increase the quality of software testing- Apply well-defined test methods through tools- Relieve the complicated and redundant work from test engineers

What do we need to automate software testing?

- Limited cost and schedule- Select and introduce quality test tools- Develop necessary effective and efficient test tools and facility - Apply well-defined testing methods and coverage- Form an integrated test environment supporting various software testing activities for products on a production line

Test Automation and Tools

Basic steps for test automation:

Level #1: Automatic test management- test case & suite management, and documentation- test script management

Level #2: Automatic test execution- black-box test control and execution- white-box test control and execution

Level #3: Automatic test generation- black-box test generation- white-box test generation

Level #4: Automatic test measurement- test coverage and metrics measurement- test cost and complexity measurement

Test Automation and Tools

Classification of software test tools:

- Program-based test tools (or white-box test tools)- Program test metrics tools- Test generation tools, such as random test tools- Program specification-based test tools

- Program regression test tools (such as program change analysis tool ) Protocol-based conformance tools

- Program performance test tools- performance monitoring tools- performance evaluation tools- Program load test tools

- GUI record and replay tools

- Test management and configuration management tools