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Unit Testing

Unit Testing Tutorial: What is, Types, Tools & Test EXAMPLE

What is Unit Testing and how does it work?
UNIT TESTING is a type of software testing in which individual units or components of a software are examined and tested separately from one another. The goal is to ensure that each unit of software code performs as expected before moving on to the next. Unit testing is performed by the developers of an application during the development (coding phase) of the application. Unit tests are used to isolate a section of code and ensure that it is correct. A unit can be a single function, method, procedure, module, or object, among other things.

Unit testing is the first level of testing performed before integration testing in the SDLC, STLC, and V Models. Unit testing is a type of WhiteBox testing technique that is typically performed by the developer in the development cycle. However, in the real world, due to time constraints or the reluctance of developers to perform unit tests, QA engineers are also responsible for performing unit tests. What is the purpose of unit testing?
Unit Testing is important because software developers sometimes try saving time doing minimal unit testing and this is myth because inappropriate unit testing leads to high cost Defect fixing during System Testing, Integration Testing and even Beta Testing after application is built. If proper unit testing is done in early development, then it saves time and money in the end.
Here, are the key reasons to perform unit testing in software engineering:

Why Unit Testing?

Unit tests help to fix bugs early in the development cycle and save costs.
It helps the developers to understand the testing code base and enables them to make changes quickly
Good unit tests serve as project documentation
Unit tests help with code re-use. Migrate both your code and your tests to your new project. Tweak the code until the tests run again.

Unit Testing: What You Need to Know
Unit Testing is a type of software testing in which developers write a section of code that tests a specific function within a software application. As a result, developers can isolate and test this function in greater depth. Doing so will reveal unnecessary dependencies between the function being tested and other units, allowing those dependencies to be eliminated. Unit testing is commonly performed by developers using the UnitTest framework to create automated test cases.

Unit testing can be divided into two categories.

Manual \sAutomated
Unit testing is typically automated, but it can also be done manually if the situation calls for it. Although there is no preference in Software Engineering for one over the other, automation is preferred. A step-by-step instructional document may be used in conjunction with a manual approach to unit testing.

How to do Unit Testing

A developer creates a section of code in an application solely for the purpose of testing a function. When the application is deployed, they would later comment out and eventually remove the test code from the application.
In addition, a developer could isolate the function in order to test it more thoroughly. When unit testing code, this is a more thorough practise that involves copy and paste of code into a testing environment separate from the natural development and testing environment. Isolating the code aids in the discovery of unneeded dependencies between the code under test and other units or data spaces in the product under consideration. These symbiotic relationships can then be severed.
When developing automated test cases, a coder typically makes use of the UnitTest Framework. To ensure that the code is correct, the developer uses an automation framework to code criteria into the test and run it against it. During the course of the test cases’ execution, the framework logs any test cases that fail. Many frameworks will also automatically flag and report, in a nutshell, any failed test cases that are encountered. It is possible that a failure will prevent further testing from taking place, depending on the severity of the failure.
Unit Testing follows a specific workflow. 1) Develop a set of test cases. 2) Review and rework 3) Establish a baseline 4) Carry out the test cases.
Unit Testing Techniques
The Unit Testing Techniques are mainly categorised into three parts which are Black box testing that involves testing of user interface along with input and output, White box testing that involves testing the functional behaviour of the software application and Gray box testing that is used to execute test suites, test methods, test cases and performing risk analysis.

The following are code coverage techniques that are used in Unit Testing:

Coverage of Statements, Decisions, Branch Coverage, Condition Coverage, and Finite State Machine Coverage are all included.
More information can be found at

Mock Objects as an Example of a Unit Test
To test sections of code that are not yet part of a complete application, unit testing relies on mock objects that are created and used to test them. Mock objects are used to fill in the gaps left by missing parts of the programme.

Example: You might be working on a function that relies on variable and object definitions that are not yet complete. In unit testing, those will be accounted for in the form of mock objects, which will be created solely for the purpose of the unit testing that will be performed on the relevant section of code.

Unit Testing Techniques

Unit testing software is available to assist with unit testing. There are several automated unit test programmes available. We’ll give you a couple of illustrations below:

Junit: Junit is a free to use testing tool for the Java programming language that is available online. It provides assertions for the purpose of identifying the test method. This tool first tests the data before it is inserted into the piece of code.
Unit testing framework NUnit is widely used for languages and can be found in all versions of Visual Studio. It is a free and open source tool that allows you to write scripts by hand. It allows you to run data-driven tests in parallel with other tests.
JMockit: JMockit is a unit testing tool that is free and open source. It is a code coverage tool that includes line and path metrics as well as other features. It enables the use of a mock API in conjunction with recording and verification syntax. Line coverage, Path coverage, and Data coverage are all provided by this tool.
Java code analysis and reporting toolkit EMMA is an open-source toolkit for analysing and reporting code written in the Java programming language. Emma supports a variety of coverage types, including method, line, and basic block. Because it is Java-based, it does not rely on any external libraries and has access to the source code of the application.

Unit Test Example: Mock Objects

PHPUnit: PHPUnit is a unit testing tool designed specifically for PHP developers. It takes small chunks of code, referred to as units, and tests each of them individually to ensure that they work properly. The tool also enables developers to assert that a system behaves in a specific way by utilising pre-defined assertion methods.
Those are just a few of the unit testing tools that are currently available. It is possible to find a unit testing tool for your programming needs regardless of the language you are using. There are many more, particularly for C and Java, but you are sure to find one for your programming needs regardless of the language you are using.
Unit Testing and Test Driven Development (TDD) are two terms that are used to describe how software is developed.
Unit testing in TDD makes extensive use of testing frameworks, which are used to automate the process. It is necessary to use a unit test framework in order to create automated unit tests. The use of unit testing frameworks is not exclusive to TDD, but they are critical to it. The following are some of the benefits that TDD brings to the world of unit testing:

Tests are written before any code is written.
Make extensive use of testing frameworks.
All of the classes in the applications are put through their paces.
It is now possible to integrate quickly and easily.
Myth: Unit testing takes a lot of time, and I’m always busy. Fact: Unit testing takes a lot of time.
My code is absolutely faultless! Unit tests are not required for me.

False assumptions are inherent in myths by their very nature. These assumptions result in a vicious cycle that looks like this:

Unit Testing Tools

Myth about UNIT Testing
The truth is that unit testing accelerates the development process.

Unit testing is often skipped by programmers because they believe that Integration Testing will catch all of their errors. Very simple errors that could have been found and fixed very quickly in unit testing take a very long time to trace and fix once the units have been integrated and tested again.

Unit Testing Has a Number of Advantages
Developers who want to learn more about the functionality provided by a unit and how to use it can look at the unit tests to gain a basic understanding of the unit API and how to use it.
Unit testing enables a programmer to refactor code at a later time while ensuring that the module continues to function correctly as a result (i.e. Regression testing). To ensure that any changes that cause a fault are quickly identified and corrected, it is recommended that test cases be written for all functions and methods in the application.
Because unit testing is modular in nature, we can test parts of the project without having to wait for other parts of the project to be completed.
Unit Testing Has Its Drawbacks
It is unrealistic to expect unit testing to catch every error in a programme. Even in the most trivial programmes, it is not possible to evaluate all possible execution paths at the same time.
Unit testing, by its very nature, is limited to a single piece of code. Therefore, it will not detect integration errors or large-scale system failures.
Unit testing should be used in conjunction with other testing activities, according to industry standards.

Test Driven Development (TDD) & Unit Testing

Using Unit Testing to Its Full Potential
Unit Test cases should be distinct from one another. Unit test cases should be unaffected by any enhancements or changes in requirements that occur.
Only one code should be tested at a time.
Unit tests should be named in a way that is easy to understand and consistent.
If you are making a change to the code in any module, make sure that the module has a corresponding unit Test Case and that the module passes the tests before making the change to the implementation.
Unit testing identifies bugs that must be addressed before moving on to the next phase of the SDLC process.
Adopt a “test as your code” approach when developing software. The greater the amount of code you write without testing, the greater the number of paths you must check for errors.