The document provides a comprehensive overview of unit testing, detailing its definition, significance, methodologies, and examples. It covers both structural and functional unit testing techniques, advantages and disadvantages, as well as various tools used in the process. Additionally, it emphasizes the importance of writing effective test cases and maintaining them as part of the software development lifecycle.

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SOFTWARE TESTING
STRATEGY—THE BIG
PICTURE
Unit Testing

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WHAT IS UNIT TESTING?
Whenever the application/module is ready (done with coding)
and given to the Test engineer, he/she will start checking every
component of the module or module of the application
independently or one by one, and this process is known as Unit
testing or components testing.

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EXAMPLE OF UNIT TESTING?
 Let us see one sample example for a better understanding of the concept
of unit testing:
This is an example of an
Online Baking
Application like HBL
Mobile App. From the
picture, it is clear that
we’ve three modules.

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 Taking in to account M1 “Amount Transfer” we will begin our unit testing
as follows:
Now, we will start
performing the unit testing
on the different components
such as
1. From account number
(FAN)
2. To account number
(TAN)
3. Amount
4. Transfer
5. Cancel

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 The Components identified will be tested as follows:
For Transfer component
1. Enter valid FAN value
2. Enter valid TAN value
3. Enter the correct value of Amount
4. Click on the Transfer button amount
→
transfer successfully
( confirmation message)
For Cancel Component
1. Enter the valid values of FAN,TAN, and
amount.
2. Click on the Cancel button a warning message should be displayed
→
about the cancellation of the transaction.

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FOR THE FAN COMPONENTS
Values Description
1234 accept
4311 Error message account valid or
→
not
blank Error message enter some
→
values
5 digit/ 3 digit Error message accept only 4
→
digit
Alphanumeric Error message accept only
→
digit
Blocked account no Error message

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While performing unit testing, we should follow
some rules, which are as follows:
To start unit testing, at least we should have one
module.
Test for positive values (validity)
Test for negative values (in-validity)
No over testing
No assumption required

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TRY TO APPLY!
As we’ve discussed earlier, that unit testing should be
applied to check for validity as well as invalidity. The
following module has been tested for validity.
1. For Transfer component
 Enter valid FAN value
 Enter valid TAN value
 Enter the correct value of Amount
 Click on the Transfer button amount transfer successfully
→
( confirmation message)
Can you try to check it for invalidity?

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 Unit Test Considerations: Unit tests are illustrated schematically in
Figure 22.3
• The module interface is tested to ensure that
information properly flows into and out of the
program unit under test.
• Local data structures are examined to ensure
that data stored temporarily maintains its
integrity during all steps in an algorithm’s
execution.
• Boundary conditions are tested to ensure that
the module operates properly at boundaries
established to limit or restrict processing.
• All independent paths through the control
structure are exercised to ensure that all
statements in a module have been executed at
least once.
• And finally, all error-handling paths are tested.

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Unit-Test Procedures. Unit testing is normally considered
as an adjunct to the coding step. The design of unit tests
can occur before coding begins or after source code has
been generated.
The unit test environment is illustrated in Figure 22.4
Stubs and drivers both are
dummy modules and are only
created for test purposes.

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 Driver is nothing more than a “main program” that accepts test-case data, passes
such data to the component (to be tested), and prints relevant results.
 Stubs (dummy subprogram) serve to replace modules that are subordinate
(invoked by) the component to be tested.
 A stub or “dummy subprogram” uses the module’s interface, may do minimal data
manipulation, prints verification of entry, and returns control to the module
undergoing testing.

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A REAL-WORLD EXAMPLE
You have written a function to add two numbers:
int Add(int a, int b) { return a+b; }
 The above function takes two numbers as input and returns their sum.
 A unit test code would look something like this:
 void TestAdd1() { Assert.IsEqual(Add(5, 10), 15) }
 The above unit test “asserts” that 5 + 10 is equal to 15. If the Add function returns anything else Assert.IsEqual
result in error and the test case will fail.
 You will probably add a few more unit test cases like these:
 void TestAdd2() { Assert.IsEqual(Add(500, 1000), 1500) }
 void TestAdd3() { Assert.IsEqual(Add(0, 1000), 1000) }
 void TestAdd4() { Assert.IsEqual(Add(-100, 100), 0) }
 void TestAdd5() { Assert.IsEqual(Add(-100, -1100), -1200) }
 After you write your test cases, you will run them to verify that everything is working correctly.

13. UNIT TESTING - EXAMPLE
Public int A(int a,int b)
{
if (a%2==0)
return a;
else
return b;
}
Public int B (int a,int b,int c)
{
int val=A(a,b);
val=A(val,c);
return val,
}
Perform UT for function A & B so that the coverage is100%

14. UNIT TESTING - EXAMPLE
Test Case ID Description Input Data Expected
Results
Actual
Results
Pass / Fail Remarks
UT-01 To test A function when a is even 2 , 3 2 2 Pass -
UT-02 To test A function when a is odd 1 , 2 2 2 Pass -
UT-03 To test B function providing any 3
values
2 , 3 , 4 2 2 Pass -
If only UT for function B is done then the coverage of function A is 50%. Why?

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UNIT TESTING TECHNIQUES

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STRUCTURAL UNIT TESTING
 Structural testing is a white box testing technique in which a developer designs test
cases based on the internal structure of the code, in a white box approach.The
approach requires identifying all possible paths through the code.The tester selects
test case inputs, executes them, and determines the appropriate output.
 Primary structural testing techniques include:
 Statement, branch, and path testing—each statement, branch, or path in a program
is executed by a test at least once.
 Conditional testing—allows a developer to selectively determine the path executed
by a test, by executing code based on value comparisons.
 Expression testing—tests the application against different values of a regular
expression.

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FUNCTIONAL UNIT TESTING
 Functional unit testing is a black box testing technique for testing the functionality
of an application component.
 Main functional techniques include:
 Input domain testing—tests the size and type of input objects and compares
objects to equivalence classes.
 Syntax checking—tests that check whether the software correctly interprets input
syntax.
 Equivalent partitioning—a software testing technique that divides the input data
of a software unit into data partitions, applying test cases to each partition.

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ERROR-BASED TECHNIQUES
 Error-based unit tests should preferably be built by the developers who originally
designed the code.Techniques include:
 Fault seeding—putting known bugs into the code and testing until they are found.
 Mutation testing—changing certain statements in the source code to see if the
test code can detect errors. Mutation tests are expensive to run, especially in very
large applications.
 Historical test data—uses historical information from previous test case
executions to calculate the priority of each test case.

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ADVANTAGES OF UNIT TESTING:
1.Unit testing allows the programmer to refine code and make sure the module works
properly.
2.Early Detection of Issues: Unit testing allows developers to detect and fix issues early
in the development process, before they become larger and more difficult to fix.
3.Improved Code Quality: Unit testing helps to ensure that each unit of code works as
intended and meets the requirements, improving the overall quality of the software.
4.Faster Development: Unit testing enables developers to work faster and more
efficiently, as they can validate changes to the code without having to wait for the
full system to be tested.
5.Better Documentation: Unit testing provides clear and concise documentation of the
code and its behavior, making it easier for other developers to understand and
maintain the software.
6.Facilitation of Refactoring: Unit testing enables developers to safely make changes to
the code, as they can validate that their changes do not break existing functionality.

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DISADVANTAGES OF UNIT TESTING:
1. The process is time-consuming for writing the unit test cases.
2. Unit Testing will not cover all the errors in the module because there is a chance of having errors in
the modules while doing integration testing.
3. Unit Testing is not efficient for checking the errors in the UI(User Interface) part of the module.
4. It cannot cover the non-functional testing parameters such as, the performance of the system, etc.
5. Time and Effort: Unit testing requires a significant investment of time and effort to create and
maintain the test cases, especially for complex systems.
6. Dependence on Developers: The success of unit testing depends on the developers, who must write
clear, concise, and comprehensive test cases to validate the code.
7. Difficulty in Testing Complex Units: Unit testing can be challenging when dealing with complex
units, as it can be difficult to isolate and test individual units in isolation from the rest of the system.
8. Difficulty in Testing Interactions: Unit testing may not be sufficient for testing interactions between
units, as it only focuses on individual units.
9. Over-reliance on Automation: Over-reliance on automated unit tests can lead to a false sense of
security, as automated tests may not uncover all possible issues or bugs.
10.
Maintenance Overhead: Unit testing requires ongoing maintenance and updates, as the code and
test cases must be kept up-to-date with changes to the software.

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UNIT TESTING TOOLS:
1.Junit: Junit is a free to use testing tool used for Java programming language. It provides assertions
to identify test method. This tool test data first and then inserted in the piece of code.
2.NUnit: NUnit is widely used unit-testing framework use for all .net languages. It is an open source
tool which allows writing scripts manually. It supports data-driven tests which can run in parallel.
3.JMockit: JMockit is open source Unit testing tool. It is a code coverage tool with line and path
metrics. It allows mocking API with recording and verification syntax. This tool offers Line
coverage, Path Coverage, and Data Coverage.
4.EMMA: EMMA is an open-source toolkit for analyzing and reporting code written in Java language.
Emma support coverage types like method, line, basic block. It is Java-based so it is without
external library dependencies and can access the source code.
5.PHPUnit: PHPUnit is a unit testing tool for PHP programmers. It takes small portions of code which
is called units and test each of them separately. The tool also allows developers to use pre-define
assertion methods to assert that a system behave in a certain manner.

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CLASS ACTIVITY 02: PRACTICE UNIT TESTING
 You can do it either individually or can make a group of 2-4 people.
 Tear a page out and write your course name and section, complete
ID, and full name on it.
 Statement: Take into consideration any online software application,
mention its name, and identify its at-least five units to perform unit
testing.
 Hint: I am not talking about the components.
 Solution: Discussed during the class.

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BOOK READING
Contents covered so far.