What is Unit Testing?

A unit test is a test that exercises a single unit of functionality in an application. It’s the software equivalent of a physical test, where you run all the same steps that you would run in your code to verify that something is working correctly. There are several benefits to writing unit tests.

Unit testing is a software development practice that improves the quality of your code by ensuring it is free from errors. This article gives you an overview of unit testing, explains how to use TDD, and introduces some best practices for effective unit testing.

What is unit testing?

In software, testing process unit testing means testing the smallest individual unit or component to validate that the smallest unit is performed as designed or not. the unit test is performed during the development or coding stage to verify its correctness, and the developers mainly perform it.

In different development methodologies like (SDLC, STLC, V Model) unit testing is the first phase of testing before doing any other testing process. Unit testing is one type of white box testing technique.

Unit testing is done by the developers during the coding to verify that the piece of written code is behaving as per the design or not. Some time by doing unit testing it helps to reduce the fixing cost during system testing, integration testing. So doing proper unit testing saves both amounts of time and investment of an organization.

How Does Unit Testing Work?

It is generally necessary to use a mock to test functions. Without mocks, it would be impossible to properly test the function. Testing is dependent on mock objects. Mock objects can be used to fill in for missing parts of a program, such as when functions require variables and/or objects that are not yet created. The purpose of a mocking library is to fill in missing functionality for an object or program unit by using objects that behave like those on which the function under test depends.

Unit Testing Techniques

The Unit Testing Techniques are mainly categorized into three parts.

White Box Testing

It is a test that focuses on the internal structure of the application and verifies particular conditions or exceptions. For example, it can be used to test boundary value cases, error conditions, and object invariants. It is also known as Glass Box Test.

Black Box Testing

It is a test that focuses on the functionality of the application and verifies functionality under certain pre-defined conditions. For example, it can be used to test pre-defined user scenarios. It is also known as Black Box Test.

Grey Box Testing

It is a combination of Black Box and White Box Testing. It focuses on the boundary value cases i.e., it verifies both functionality and internal structure.

There are different Code coverage techniques used in Unit Testing. we have noted down various Code coverage techniques:

Statement Coverage: This technique is used to test the lines of code executed when a program is run, along with the branches (decisions) taken by those lines of code.

Branch Coverage: This technique is used to test the condition under which each branch in a program is executed. Each branch is a decision in the code, such as an if-else statement or switch statement, and sometimes also includes loops.

Decision Coverage: This technique is used to test the different decisions made in a program, along with their associated conditions.

Condition Coverage: This technique is used to test each of the conditions that cause a particular branch in a program, along with its associated branches.

Finite State Machine Coverage: This technique is used to test each of the states in a program’s internal finite state machine.

Unit Testing Advantage

As unit testing is carried at a very beginning level so the issue can be found at an early stage. So that defects can fix early before impacting any other piece of code.

For making unit testing, possible codes need to be modular. This means that codes are easier to reuse, and it also helps to reuse the same code in other require places, so because of this nature, the development also goes faster.

Because unit testing helps to reduce the cost of bug fixes as compared to you finding a bug in system testing or integration testing. You are also debugging easy because when a test fails only, you need to debug the latest changes.

By unit testing, the quality of the code is improved because it identifies the defect before the code goes for integration testing.

Test automation is one of the best practices that can increase your application’s stability, reduce costs, and ensure good overall performance. Automated testing minimizes errors so that defective products do not reach customers. By eliminating these defects early in the process, automated testing helps prevent expensive recalls and costly fixes. It also ensures consistent reliability for all users by allowing independent defects to be found as soon as they occur.

Advantages of Unit Testing:

• Provides detailed information about how individual units function when combined with other units;
• Identifies errors or faults before the final product is released;
• Provides a stable, maintainable design;
• Affords better documentation of code behavior.

Other Benefits include: Developing code with good test cases makes it easier to refactor or restructure the system in order to improve the overall quality without affecting existing functionality. It also helps avoid regression bugs that might otherwise be introduced during the process of upgrading and debugging production systems.

Unit Test Disadvantage

Unit testing can’t be expected to catch every error of a program. Because it is not possible to test all possible paths of the program. In unit testing, we are trying to find the errors from a specific unit of code. So here we can’t found integration errors or system-level errors.

• Test procedures are generally “informal”, so there is no standard way to write them;
• They tend to be written by developers who understand the application internals, but not necessarily how they will interact with each other in different situations; 3-There are often only enough tests to guarantee correct behavior of units in isolation, not the proper integration of all units into a complete application.

The main problem with unit testing is that it doesn’t guarantee 100% correctness and it can only be used to test code written so far. To catch any errors introduced by later modifications, new tests must be added after each modification. This means that more time and money are required to develop software using this approach – especially when compared to traditional top-down development methods like Waterfall or pseudo-Agile approaches like Scrum (which completely ignore Automated Testing).

Facts About the Unit Test

• Unit test cases should be independent, and it should not impact any requirement change or enhancement.
• The naming convention for each unit test case should be clear and easy to understand.
• There should be a unit test case for each module, and before implementing the change into the module, the module should pass the test.
• Bugs found during the unit test cases should be fixed before going to the next phase.
• Try to cover all paths through the unit test cases and give more attention to the loop conditions.
• Always use a version control system so that you can easily track the changes of your script.
• Perform the unit tests more frequently and continuously.

How to Write Unit Tests?

You SHould always need to write the unit tests with the code so that the developer who is working on the application can understand what is written there. For writing unit tests, there is a standard rule for that. The testing is derived from a test case and that much not dependent on other tests.

When you write the test method for every test that should start with a test, for each operation like reading, click, download, delete there should be separate methods for each.

Below you can get such a list of methods:

• setUp: this method is used to prepare the tests, so before every test, this method is called.
• tearDown: this method is called at last of test execution that is after all test methods have been called, and the respective result is stored. this method can also be called when an exception occurs.
• setUpClass: this method is called before an individual class called.
• tearDownClass: this method is called when individual methods of a class are completed
• setUpModule: this method is called before the classes of an individual module run.
• tearDownModule: this method is called after the classes of an individual module run.

By following such things, we can able to write good unit tests.

Unit Testing Tools

Unit testing is usually done by a programmer using a unit testing tool. These tools provide the actual framework to run individual tests and collate their results. Some unit testing frameworks provide test cases within the source code, allowing for greater integration into an IDE. There are open source and commercial tools available:

Here are some of the unit testing tools which are broadly used to perform the unit testing.

junit

It is a set of classes that allow developers to create repeatable tests. It was originally created for Java, but it can be used with other languages.

It is a unit testing framework for Python, using the XUnit design pattern and inspired by JUnit. It can be used with Python or any other language that allows the definition of classes and methods.

NUnit

NUnit is a lightweight, free and open-source unit test framework for all .NET programming languages. It was originally created by Novell in 2002 and was donated to the community in 2005.

JMockit

Jmockit is a Java mocking framework for unit testing and behavior-driven development. It can be embedded in any JVM language that has a JSR-223 (Java API for XML-based RPC) implementation.

It is an open-source unit testing framework by Google and inspired by JUnit, with features for testing Google-specific libraries and code. It uses annotations to specify test cases in the source code.

unittest2

It is a unit testing framework for Python. It’s implemented on top of the standard unittest module and provides additional utilities that make testing easier. It is a Python port of the popular JUnit framework by Sun Microsystems.

TestNG: It is an open-source framework for writing and executing automated tests of Java code. It was previously known as Novlet and TestNg, with its current name valid since 2005.

TestNG was designed to be a simple framework that could provide both easy extensibility and a powerful set of features, such as the synchronization of tests or the option to run only relevant tests, for example. It is developed by Apache Software Foundation and used in Java projects such as Hibernate, Apache Ant, and Apache Camel.

Conclusion

As you can see, there is a lot of involvement in unit testing. It can be simple or complex that depending upon which type of application you’re going to test and what testing strategy you are going to follow. But you can’t ignore the importance of unit testing in the software development process.

Unit testing is widely used in the software development industry. The fact that every developer can use it to run test cases or capture exceptions and debug information is a significant advantage. It helps in finding bugs early and preventing the need for large-scale testing of the already developed software.

Testing is extremely important in ensuring that the software works as designed, but it is not a replacement for good development practices. Many unit testing frameworks will produce false failures unless additional steps are taken to design for testability.

Developers should learn testing principles and get used to the process of writing tests to ensure that they exercise the application code properly. When writing tests, developers should ensure that they are not testing the framework or platform itself but are actually testing the functionality of their application.

Unit testing is an iterative process and requires the involvement of all members of the development team, from testers and designers to developers themselves. It improves the design of software and increases the confidence in a product by identifying bugs early on.

Unit testing is no replacement for good design, integration, or end-to-end testing, but rather a complement to them.

After every iteration of the software development lifecycle, unit testing is an important practice that ensures high-quality software.

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