Intro to Software Testing

8/2/2019 Intro to Software Testing

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Software Testing

Presenter :

Ambili P K


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Sources of Problems Requirements Definition: Erroneous, incomplete,

inconsistent requirements.

Design: Fundamental design flaws in the software. Implementation: Mistakes in chip fabrication, wiring,

programming faults, malicious code.

Support Systems: Poor programming languages, faulty

compilers and debuggers, misleading development tools.


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Sources of Problems (Contd) Inadequate Testing of Software: Incomplete testing,

poor verification, mistakes in debugging.

Evolution: Sloppy redevelopment or maintenance,introduction of new flaws in attempts to fix old flaws,

incremental escalation to inordinate complexity.


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How to define Software

Testing Principles Testing

The execution of a program to find its faults

VerificationThe process of proving the programs correctness.

Validation

The process of finding errors by executing the programin a real environment

Debugging

Diagnosing the error and correct it


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Principles of Testing Testing must be traceable to the requirements.

Testing should be planned for early in a software process.

Testing efforts should be based on data about the errorsdetected.

Testing should be incremental.

Testing should focus on exceptions.

Debugging should be planned for separately so that there isenough time and budget to understand and resolve bugs.


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What are the Types of

Software Tests Unit Testing (White Box)

Integration Testing

Function Testing (Black Box)

Regression Testing

System Test

Acceptance and Installation Tests


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Unit Testing (White Box) Individual components are tested.

It is a path test.

To focus on a relatively small segment of codeand aim to exercise a high percentage of the

internal path

Disadvantage: the tester may be biased byprevious experience. And the test value may not

cover all possible values.


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White-box techniques: These are based onknowledge of the program structure and are used

to check for logical mistakes. Black-box techniques: These are used to test

software as a whole and do not depend on the

internal design and structure of the software.


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Integration Testing Top-down Integration Test

Bottom-up Integration Test


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Top-down Integration Test The control program is tested first. Modules are

integrated one at a time. Emphasize on interface

testing

Advantages: No test drivers needed

Interface errors are discovered early

Modular features aid debugging

Disadvantages:

Errors in critical modules at low levels are found late.


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A

B

T1

T2

T3

A

B

C

T4

T3

T2

T1

Top-down Testing


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Bottom-up Integration Test Allow early testing aimed at proving feasibility

Emphasize on module functionality and performance

Advantages:Errors in critical modules are found early

Disadvantages: Test drivers are needed

Interface errors are discovered late


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TestDrivers

Level N

Level N-1 Level N-1

Level NLevel N

TestDriversTestDrivers

TestDrivers

TestDrivers

Bottom-up testing


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Function Testing (Black Box) Designed to exercise its external specifications

Testers not biased by knowledge of the programs

design. Disadvantages:

1. The need for explicitly stated requirements

2. Only cover a small portion of the possible test

conditions.


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Regression Testing Test the effects of the newly introduced changes on

all the previously integrated code.

The common strategy is to accumulate acomprehensive regression bucket but also to definea subset.

The full bucket is run only occasionally, but the

subset is run against every spin. Disadvantages:

1. To decide how much of a subset to use and whichtests to select.


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What is Test Planning Define the functions, roles and methods for all test

phases.

Test planning usually start during the requirementsphase.

Major test plan elements are:

1. Objectives for each test phase

2. Schedules and responsibilities for each test activity3. Availability of tools, facilities and test libraries.

4. Set the criteria for test completion


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Test Execution & Reporting Testing should be treated like an experiment.

Testing require that all anomalous behavior be noted

and investigated. Big companies keep a special library with all copies of

test reports, incident forms, and test plans


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Real-Time Testing Real-Time testing is necessary because the deployment

system is usually more complicate than developmentsystem

Rules apply for testing real time system1. Evaluate possible deadlocks, thrashing to special timing

conditions

2. Use tests to simulate hardware faults.

3. Use hardware simulation to stress the software design.4. Design ways to simulate modules missing in the

development system.


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Limitations of Software Testing Testing cannot be exhaustive.

Selective testing cannot detect all errors.

Testing itself may have bugs.

Testing cannot prevent errors; it only detects them.

Testing is not as cost-effective as other quality filters

such as formal technical reviews because it comeslate in the cycle when errors are more in number

and costlier to rectify.

Documents

Intro to Software Testing