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Software Testing and Quality Assurance

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Software Testing and Quality Assurance Lecture 29 - Introduction to Software Testing Lecture Outline Introduction to testing types. Testing activities. – PowerPoint PPT presentation

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Title: Software Testing and Quality Assurance


1
Software Testing and Quality Assurance
  • Lecture 29 - Introduction to Software Testing

2
Lecture Outline
  • Introduction to testing types.
  • Testing activities.
  • Introduction to test cases, test oracles and
    their execution.

3
Testing Policy
  • Only exhaustive testing can show a program is
    free from defects. However, exhaustive testing is
    impossible
  • Testing policies define the approach to be used
    in selecting system tests For example,
  • All functions accessed through menus should be
    tested
  • Combinations of functions accessed through the
    same menu should be tested
  • Where user input is required, all functions must
    be tested with correct and incorrect input.

4
Software Testing Development Life Cycle
Requirements
System Testing
Integration Testing
Architectural Design
Unit Testing
Detail Design
Implementation
5
Unit Testing
module to be tested
results
software engineer
test cases
6
Unit Testing
module to be tested


interface
local data structures

boundary conditions
independent paths

error handling paths
test cases
7
Unit Testing
driver

interface
local data structures

Module
boundary conditions
independent paths

error handling paths
stub
stub
test cases
RESULTS
8
Integration Testing
  • Involves building a system from its components
    and testing it for problems that arise from
    component interactions.
  • Top-down integration
  • Develop the skeleton of the system and populate
    it with components.
  • Bottom-up integration
  • Integrate infrastructure components then add
    functional components.

To simplify error localisation, systems should
be incrementally integrated.
9
Integration Testing
  • The Big-bang Approach.
  • Incremental Approach.

10
Top-Down Integration
A
top module is tested with
stubs
B
F
G
stubs are replaced one at
a time, "depth first"
C
as new modules are integrated,
some subset of tests is re-run
D
E
11
Bottom-Up Integration
A
B
F
G
drivers are replaced one at a
time, "depth first"
C
worker modules are grouped into
builds and integrated
D
E
cluster
12
Thread-Based Integration
A
Top modules are tested with stubs
B
F
G
C
Worker modules are grouped into
builds and integrated
D
E
cluster
13
System Testing
  • System Functional Test
  • Test entire system against the functional
    requirements.
  • System Performance Test
  • Test the non-functional requirements of the
    system. For example,
  • Response times, load testing etc.
  • System Acceptance Test
  • Set of tests that the software must pass before
    it is accepted by the client.

14
Trivial Example
  • You have been asked to write a term paper on
    Integration Testing in Component Based System.
    To do this, you need to find references from a
    range of library databases.
  • You logs on to the KFUPM library system and uses
    the search facility to find relevant papers from
    IEEE, ACM and Elsevier databases.
  • One paper of special interest requires
    authentication and you have to fill an online
    form to receive the paper.
  • If you are allowed, the paper will be downloaded
    and ready for collection.
  • An email will be send to you once the paper is
    ready.

Scenario-based Testing
15
Student Activity
  • Identify the possible interactions for the system
    testing of library system.

16
Trivial Example - System Testing
  • Test the login mechanism using correct and
    incorrect login.
  • Test the search facility using queries against
    known source to check that the search mechanism
    is actually documents.
  • Test system presentation facility to check that
    information about documents is displayed
    properly.
  • Test the mechanism to request permission for
    downloading.
  • Test the e-mail response indicating that the
    download document is available.

17
Regression Testing
  • Change do not always effect the entire program.
  • Change in one part of system can effect other
    part.
  • After each change
  • Entire test suite of a system must be run again.

Need for an automatic test suite execution.
18
Test Activities
  • Boils down to selecting and executing test cases.
    Test case consists of
  • Set of test inputs, of if the program is
    non-terminating, a sequence of test inputs.
  • Expected results when the inputs are executed
    and
  • Execution conditions or execution environment in
    which the inputs are to be executed.

These steps generally remain same from unit
testing to system testing.
19
Test Case Selection
  • Coverage criterion
  • Equivalence Partitioning
  • Boundary-Value Analysis
  • Coverage-Based Testing
  • Control-flow
  • Data-flow
  • Expected behavior of every test input to be
    generated. (Test Oracles)
  • Testing environment.

20
Test Oracles
  • Determines whether or not the program has passed
    or failed the test case.
  • A test oracle is
  • A program
  • A process
  • A body of data
  • In many cases - directly form the requirements.
  • For example, a test case assessing performance -
    performance threshold.

Difficult to automate or to assess their quality
21
Test Execution
  • Test inputs on the program-under-test
  • Record the actual behavior.

Generally can be automated to an extend !!!!
22
Test Evaluation
  • Compare the actual behavior with the expected
    behavior.

Generally can be automated to an extend !!!!
23
Test Reporting
  • Report the outcome of the testing.
  • Developers
  • Project Mangers etc.

Generally can be automated to an extend !!!!
24
Key Points
  • A system typically undergoes a range of testing
    types.
  • Each type of testing is aimed at detecting
    different kinds of failures.
  • Testing boils down to the selection and execution
    of test cases.
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