Software Testing & Its TechniquesBy : Shah Rukh Rayaz

Software Testing

• Software testing is an investigation conducted to provide

stakeholders with information about the quality of the

product or service under test. Software testing can also

provide an objective, independent view of the software to

allow the business to appreciate and understand the risks of

software implementation.

• Software testing can be stated as the process of validating

and verifying that a software program/application/product.

• Meets the requirements that guided its design and

development.

Programmer Vs Tester

• Software testing, depending on the testing method employed, can

be implemented at any time in the development process. However,

most of the test effort occurs after the requirements have been

defined and the coding process has been completed. As such, the

methodology of the test is governed by the software development

methodology adopted.

• A good test has a high probability of finding an error.

• A good test should be neither too simple nor too complex.

• A good test is not redundant

• A study conducted by NIST in 2002 reports that software bugs cost

the U.S. economy $59.5 billion annually. More than a third of this

cost could be avoided if better software testing was performed.

• The software testing team

• software testing is a part of the software quality assurance (SQA)

process.

Functional vs non-functional testing

• Functional testing refers to activities that verify a specific action or function of

the code. These are usually found in the code requirements documentation,

although some development methodologies work from use cases or user

stories. Functional tests tend to answer the question of "can the user do this"

or "does this particular feature work."

• Non-functional testing refers to aspects of the software that may not be

related to a specific function or user action, such as scalability or other

performance, behavior under certain constraints, or security. Non-functional

requirements tend to be those that reflect the quality of the product,

particularly in the context of the suitability perspective of its users.

Static vs. dynamic testing

• There are many approaches to software testing. Reviews,

walkthroughs, or inspections are considered as static testing,

whereas actually executing programmed code with a given

set of test cases is referred to as dynamic testing

Software verification and validation

• Verification:

Are we building the Product Right. or

Have we built the software right? (i.e., does it match the

specification).

• Validation:

Are we building the Right Product. Or

Have we built the right software? (i.e., is this what the

customer wants).

Unit testing

Unit testing, also known as component testing, refers to tests that verify the

functionality of a specific section of code.

Integration testing.

Integration testing is any type of software testing that seeks to verify the interfaces

between components against a software design.

1) Top-down integration.

i. Depth-first integration

ii. Breadth –first integration.

2) Bottom-up integration.

Top-down integration.

• Is an incremental approach to construction of the software

architecture.

• Modules are integrated by moving downwards by.

i. Depth-first integration

ii. Breadth –first integration.

– Depth-first integration would integrate all components on a

major control path of the structure

– Breadth-first integration incorporates all components directly

subordinate at each level, moving across the structure

horizontally .

Bottom-up integration testing

0. Low level components are combined in clusters that perform a specific software

function.

1. A driver (control program) is written to coordinate test case input and output.

2. The cluster is tested.

3. Drivers are removed and clusters are combined moving upward in the program

structure.

Regression testing

• Regression testing is the process of testing changes to

computer programs to make sure that the older programming

still works with the new changes.

• Smoke Testing

Smoke testing is done for the software in order to verify that

the software is stable enough for further testing. it has a

collection of written tests .

System Testing• Series of different tests whose primary purpose is to full

exercise the computer based system.

1) Recovery Testing

– Software fails in various ways

– MTTR

2) Security Testing

Hackers

3) Stress Testing. (abnormal conditions)

Ten Interrupts per second, when one or two is the average

rate.

• 4) Performance Testing– Coupled with stress testing

Alpha & Beta Testing• Acceptance Testing

1. Alpha testing occurs before beta testing.

2. Alpha testing clears out most of the major bugs in a program while beta

testing is more like polishing the program.

3. Alpha testing is often not open to the public while beta testing can

often involve the public

Software Bug

• A software bug is the common term used to describe an

error, flaw, mistake, failure, or fault in a computer program.

The box approach

Software testing methods are traditionally divided into white-

and black-box testing. These two approaches are used to

describe the point of view that a test engineer takes when

designing test cases.

1)White-box testing2)Black –box testing

White-box testing/Glass Box

• Using white-box testing method, the software engineer can

derive test cases that

i. Guarantee that all independent paths within a module have

been exercised at least once.

ii. Exercise all logical decision on their true & false sides

iii. Execute all loops at their boundaries vales.

iv. Exercise internal data structure.

Basis Path Testing

• Each circle, called a flow graph node, represents one or more procedural statements..

• The arrows on the flow graph, called edges or links, represent flow of control .

• An edge must terminate at a node, even if the node does not represent any procedural statements.

• Areas bounded by edges and nodes are called regions. When counting regions, we include the area outside the graph as a region. Each node that contains a condition is called a predicate node

Independent Program Path • An independent path is any path through the program that introduces at least one

new set of processing statements or a new condition. When stated in terms of a

flow graph, an independent path must move along at least one edge that has not

been traversed before the path is defined.

• For example, a set of independent paths for the flow graph illustrated in above Figure is:

• path 1: 1-11

path 2: 1-2-3-4-5-10-1-11

path 3: 1-2-3-6-8-9-10-1-11

path 4: 1-2-3-6-7-9-10-1-11

• Note: The path 1-2-3-4-5-10-1-2-3-6-8-9-10-1-11 is not considered to be an independent path

how many paths ?

Simply computed in one of three ways:

• The number of regions of the flow graph correspond to the

cyclomatic complexity.

• Cyclomatic complexity, V(G), for a flow graph, G, is defined as

V(G) = E - N + 2 where E is the number of flow graph edges, N

is the number of flow graph nodes.

• Cyclomatic complexity, V(G), for a flow graph, G, is also

defined as V(G) = P + 1 where P is the number of predicate

nodes contained in the flow graph G.

• The flow graph has four regions.

• V(G) = 11 edges - 9 nodes + 2 = 4.

• V(G) = 3 predicate nodes + 1 = 4.

Black Box Testing• Also called behavioral testing.

• Focuses on functional requirements for a software.

• BBT is not an alternative to WBT.

• It is complementary approach that is likely to uncover a

different class of errors than WBT.

• Black box Testing attempts to find errors in the following

categories.

Categories

1. Incorrect or missing functions.

2. Interface errors.

3. Errors in data structure or external data base access.

4. Behavior or performance errors.

5. Initialization & termination errors.

Testing Principles

1. All test should be traceable to customer requirements.

2. Tests should be planned long before testing begins.

3. The Pareto principle applies to software testing.

4. Testing should begin “in the small” and progress toward

testing “in the large”.

5. Exhaustive testing is not possible.

Reference

• Software Engineering (A Practitioner’s Approach Six Edition)

By Roger S. Pressman. (Chapter No 5,13,14).

• http://en.wikipedia.org/wiki/softwaretesting.

Q & A