Coding and testing In Software Engineering

Dr. Satya Bhushan Verma
Assistant Professor

 Coding Standard and Guidelines
 Code Review
 Code walk-through
 Code inspection
 Testing
 Design of Test Cases
 Black-box testing
 White Box testing

 Good software development organization usually develop there own coding
standard and guidelines depending on what beat suit their needs and the types of
products they develop.

 Do not use coding style that is too clever or too difficult to understand.
 Avoid obscure side effect.
 Do not use an identifier for multiple purpose
 The code should be well documented.
 Do not used GOTO statement.

 Code review for a module is carried out after the module is successfully compiled
and all the syntax errors eliminated. Code reviews are extremely cost-effective
strategies for reduction in coding errors in order to produce high quality code.
1. Code walk-through
2. Code inspection

 Code walk-through is an informal code analysis technique. In this technique, after
a module has been coded, it is successfully compiled and all syntax errors are
eliminated.
 The main objectives of the walk-through are to discover the algorithmic and
logical errors in the code.

 the aim of code inspection is to discover some common types of errors caused due
to oversight and improper programming.
 The following is a list of some programming errors which can be checked
during code inspection:
 Use of uninitialized variables
 Jumps into loops
 Nonterminating loops
 Incompatible assignments
 Array indices out of bounds
 Improper storage allocation and deallocation
 Mismatches between actual and formal parameters in procedure calls
 Use of incorrect logical operators or incorrect precedence among operators

 Testing a program consists of subjecting the program to a set of test inputs (or test
cases) and observing if the program behaves as expected.
 The following are some commonly used terms associated with testing.
1. A failure is a manifestation of an error (or defect or bug). But the mere presence
of an error may not necessarily lead to a failure.
2. A test case is the triplet [I, S, O], where I is the data input to the system, S is
the state of the system at which the data is input, and O is the expected output
of the system.
3. A test suite is the set of all test cases with which a given software product is to
be tested.

 Following is simple programming error.
If (x>y) max = x;
else max = x;
 The test suite ((x = 3. y = 2); (x = 2, y = 3)) can detect the error
 whereas a larger test suite ( (x = 3, y = 2); (x = 4, y = 3); (x = 5, y = 1)] does not
detect the error.

 Two main approaches to systematically designing test cases
1. Black-box approach
2. White-box (or glass-box) approach

 In black-box testing test cases are designed from an examination of the
input/output values only and no knowledge of design or code is required.
 The following are the two main approaches to designing black-box test cases.
1. Equivalence class partitioning
2. Boundary value analysis

 The following are some general guidelines for designing the equivalence classes
1. If the input data values to a system can be specified by a range of values, then
one valid and two invalid equivalence classes should be defined.
2. If the input data assumes values from a set of discrete members of some
domain, then one equivalence class for valid input values and another for
invalid input values should be defined.

 For a software that computes the square root of an input integer which can
assume values between 0 and 5000, there are three equivalence classes: The set of
negative integers, the set of integers in the range between 0 and 5000, and the
integers larger than 5000. Therefore the test cases must include representative
values from each of the three equivalence classes and a possible test set can
therefore be: [-5, 500, 6000)

 Boundary testing is the process of testing between extreme ends or boundaries
between partitions of the input values.
 Extreme ends like Start- End, Lower- Upper, Maximum-Minimum, Just Inside-
Just Outside values are called boundary values and the testing is called
"boundary testing".
1. Minimum
2. Just near the minimum
3. Just near the maximum
4. Maximum

 For a function that computes the square root of integer values in the range
between 0 and 5000.
 The test ceases are ( 0, -1, 1, 5000, 4999, 5001 ).

 There are several white box testing strategies. Each testing strategy is based on
some heuristic.

 The statement coverage strategy aims to design test cases so that every statement
in a program is executed at least once.
 The principal idea governing the statement coverage strategy is that unless we
execute a statement, we have no way of determining if an error exists in that
statement. Unless a statement is executed, we cannot observe whether it causes
failure due to some illegal memory access, wrong result computation, etc.

int compute_gcd (x, y)
int x, y;
{
while (x != y){
if (xx>y) then
x=x-y
else y=y-x;
}
return x;
}
By choosing the test set ( (x=3, y=3).(x=4. y=3), (x=3, y=4) ). we can exercise the program
such that all statements are executed at least once.

 In the branch coverage-based testing strategy, test cases are designed to make
each branch condition assume true and false values in turn.
 Branch testing is also known as edge testing as in this testing scheme, each edge
of a program's control flow graph is traversed at least once.
 Testcases for branch Coverage [(x=3, y=3).(x=3. y=2), (x=4, y=3). (x=3, y=4))

 The path coverage-based testing strategy requires us to design test cases such
that a linearly independent paths in the program are executed at least once. A
linearly independent path can be defined in terms of the control flow graph (CFG)
of a program.

Coding and testing In Software Engineering

Coding and testing In Software Engineering

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