se software coding and testing 150407

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Software Coding and Testing

by:Bharat V. Chawda

Computer Engineering Department,BBIT, VVNagar

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Overview Introduction Code Review Software Documentation Testing Test Documentation

(As per GTU Curriculum – Diploma in Computer/IT Engineering)

Based on Books:1. Fundamentals of Software Engineering – by Rajib Mall2. Software Engineering: A Practitioner’s Approach – by Roger

Pressman

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Introduction: Coding When?

After: Design phase is complete, and Design docs are successfully reviewed

Objective Design of System Code in high-level

lang Unit test this code

Coding Standards Coding Guidelines

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Code Review When?

After: Module successfully compiles All the syntax errors have been

eliminated Code review v/s Testing

Code Review: Cost-effective strategy for error elimination Direct detects errors

Testing: Detects failures only: diff i/p, circumstances Requires efforts: Debugging – locate errors;

Error Correction – fix the bug CR: Two Types

Code Walkthrough, Code Inspection

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Code Walkthrough Informal code analysis technique When to review?

After: Module is Coded, Compiled, and Syntax Errors are eliminated

How? Few members of dev team are assigned this

task Each member selects some test cases Simulate execution of code by hand (Trace execution through different Statements

and Instructions of the code) Note down findings; Discuss with coder in WT

meeting

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Code Walkthrough (cont) Objective

Discover the algorithmic and logical errors in the code

Guidelines Team size: Not too big, not too small: 3-7

member Focus on discovery of errors, not on how

to fix them Managers should not attend WT meeting

– To avoid feeling: engineers are being evaluated

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Code Inspection Code is examined for the presence of

some common/classical programming errors

Use of uninitialized variables Incompatible assignments Non terminating loops; Jumps into loops;

Improper modification of loop variables Mismatch in arguments in procedure

(fun) calls Array indices out of bounds Improper storage allocation and de-

allocation Use of incorrect logical operators;

Precedence Comparison of equality of floating point

values

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Code Inspection (cont) Objective:

Check for the common types of errors Check whether coding standard have

been adhered to

SW companies can maintain list of commonly committed error check list for code inspection

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Software Documentation SW Product

Executable files + Source Code + Documents

Documents: Users’ manual, SRS doc, Design doc, Test doc, Installation manual, etc

Why required? Enhances understandability of SW

product; Reduces effort & time required 4 maintenance

Help users to und & effectively use the system

Help in effectively tackling manpower turnover

Help manager to effectively track progress

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SW: Internal Documentation Code comprehension features:

provided in the source code itself Comments embedded in the source code Use of meaningful variable names Module and function headers Code indentation Code structuring (modules + functions) Use of constant identifiers Use of enumerated types Use of user-defined data types

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SW: External Documentation Contains various types of supportive

docs Users’ manual SRS doc Design doc Test doc Installation manual…

Features: Good external documentation

Consistency Understandability

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Testing: Introduction Testing:

Aim: Identify all defects in a program Error / Defect / Bug / Fault:

Mistake committed by development team during any of the development phases.

Failure: Manifestation of an error Symptom of an error

Test case: Triplet [I, S, O]: I/P, State, O/P

Test suite: Set of all test cases…

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Testing: Levels/Stages Unit Testing Integration Testing System Testing

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Unit Testing When?

After: Module has been coded and reviewed

How? Design test cases Develop Environment Do testing

Environment Driver + Module + Stub

(Stub: Dummy procedures with simplified behavior)(Driver: Non-local data str + Code to call fun of

module)

Driver

Stub

Module under Test

Global Data

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Black Box Testing Concept

Based on functional specification of SW Based on functional behavior:

Inputs/Outputs Also known as: Functional Testing No knowledge of design & code is

required

Two main approaches Equivalence Class Partitioning Boundary Value Analysis

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Black Box Testing: Example SW: Computes square root of

integer values in the range of 0 and 5000.

Test Cases: Equivalence Class Partitioning {-5, 500, 6000}

Test Cases: Boundary Value Analysis {-1, 0, 5000, 5001}

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White Box Testing Concept

Based on analysis of code Based on structure of the implementation Also known as: Structural Testing Knowledge of design & code is required

Two Types Fault based: Targets: detect certain types

of F Coverage based: Targets: execute (cover)

certain elements of a program

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White Box T: Coverage based Strategies

Statement Coverage Each statement should be executed at least

once

Branch Coverage Each branch : traversed at least once

Condition Coverage Each condition : True at least once and false

at least once

Path Coverage Each linearly independent path : executed at

least once

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White Box T: Example

int test (int x, int y)

{ int z;

z = -1;

if (x>0 && y>0)

z = x;

return z;

}

Statement Coverage:

{(x=1,y=1)}

Branch Coverage:

{(1,1), (0,0)}

Condition Coverage:

{(0,0), (0,1), (1,0), (1,1)}

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White Box T: Path Coverage Concept

All linearly independent paths in the program are executed at least once

CFG: Control Flow Graph Directed graph – consisting of a set of

Nodes (N) and Edges (E) where Nodes (N): corresponds to a unique

program statement Edges (E): Transfer of control From one

node to another node

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White Box T: Path Coverage Example:

int gcd (int x, int y){

while (x!=y) {

if (x>y) x=x-y;

else y=y-x;

} return x;

}

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White Box T: Path Coverage Example:

int gcd (int x, int y){

1. while (x!=y) {

2. if (x>y)3.

x=x-y;else

4. y=y-x;

5. }6. return x;

}

CFG:

1

2

3 4

5

6

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Cyclomatic Complexity Metric V(G) = E – N + 2

V(G) = Total number of non-overlapping bounded areas + 1

V(G) = Total number of non-overlapping areas

V(G) = Decision Points + 1

V(G) = Predicate Nodes + 1

Cyclomatic Complexity of previous example of GCD: 3

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Test Documentation When: Towards end of testing Represents: Test summary report Specifies:

Total number of tests: applied to a sub-system

How many tests were successful How many tests were unsuccessful; and

at which extent (degree): totally or partially

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Thank-U…!!!

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