Unit Testing: A Detailed Guide

What is Unit Testing?

Unit testing is the process of testing small isolated portions of a software application called units. Unit testing is a method of testing small pieces of a software application without relying on a third-party system. Any component that interacts with an external database, files, or the network cannot be checked as part of unit testing. Unit tests primarily test isolated components during the product’s early development phase.

Developers using frameworks like Nodejs, Angular, etc., employ Unit Testing Frameworks.

What is Application Unit Testing?

During an application’s development phase, developers typically perform unit testing. When a piece of code is written to carry out a specific function, there must be a means to check and prove that the implementation is correct. Hence, tests are required.

• At several stages, tests are required at the application and the integration levels of different components, classes, and interfaces.
• Using parameterized tests can help you write and manage unit tests faster. These allow a single test to be run numerous times with varied input sets, decreasing the amount of test code duplication.

Unlike traditional unit tests, which are usually closed methods with test invariant conditions, Parameterised tests accept any set of parameters. TestNG, JUnit, and its .Net cousin, XUnit, all support parameterized tests. Parameters for unit tests can be entered manually or produced automatically by the test framework in some situations. 

Testers can perform unit testing with various frameworks. For instance, in NodeJS, there is Mocha, Jest, and Jasmine. Unit testing is also done by developers using NodeJS, Angular, and other frameworks.

Why perform Unit Testing of Applications?

• The primary goal of Unit testing is to isolate written code to test and establish if it works as intended.
• Unit testing is a crucial phase in the development phase because, if executed properly, it can assist in uncovering early faults in code that may be more difficult to detect in subsequent testing stages.

Unit Testing Techniques

The process of unit testing can be carried out with the help of three main testing techniques:

• Structural Technique

Structural testing is a sort of testing that examines the structure of a program. It’s often referred to as White Box or Glass Box testing. Because this type of testing necessitates a thorough understanding of the code, developers typically perform it. It concerns more about how the system accomplishes it than its functioning. It expands the scope of the tests.

• Functional Testing Technique

Functional testing is a sort of testing that aims to determine whether each application feature functions in accordance with the program requirements. The result of each function is compared to the relevant requirement to see if it meets the end user’s expectations. The testing is carried out by supplying sample inputs, recording the resulting outputs, and ensuring that the actual outputs match the expected outputs.

• Error based Technique

The person who designed the code must be involved in the process as they are the ones who know the code end-to-end. The following are a few examples of error-based techniques:

• Historical Test Data: This technique uses historical data from previous executions of the test case to determine the priority of each test case.
• Mutation Testing: This involves changing some statements in your source code and seeing if your test code can discover the mistakes.
• Fault seeding techniques: This can be used to introduce known problems into the code and test them until all of them are identified.

Introduction to Test-Driven Development (TDD)

Test-Driven Development or TDD is a software development method in which test cases are written to outline and evaluate how the code will perform. To put it another way, test cases for each capability are generated and tested first, and if the test fails, new code is written to pass the test, keeping the code simple and bug-free.

Test-Driven Development and building tests for each tiny feature of an application is the first step in the development process. The TDD framework tells developers to build new code only if an automated test fails, avoiding code duplication.

Relationship of Test Driven Development (TDD) & Unit Testing

Unit testing is an automated procedure for ensuring that even minor code components are working correctly. Unit testing is done on an individual basis, which means you can write a unit test at any point during the application development process.

Whereas TDD is a method of producing code to create a tested design. This procedure entails simultaneously writing the code and the tests for it. Furthermore, this procedure is carried out on a larger scale, implying that the TDD cycle must be repeated numerous times before a working feature is obtained.

Best Practices in Unit Testing

• Write tests during development, not after it

Unit tests are the first tests performed in the development cycle and are at the bottom of the testing pyramid. Hence, they perform best when they are run concurrently with development rather than afterward.

Setting up unit tests as soon as feasible encourages the production of clean code and the early detection of issues.

Writing tests at the end of development may result in untestable code; on the other hand, writing tests concurrently with production code allows us to evaluate both test and production code simultaneously, which helps developers understand the code better. It also makes the unit testing process more scalable and long-term.

• In tests, don’t use reasoning.

Using logical conditions and manual string concatenation in unit tests increases the likelihood of defects in your test suite. Instead of focusing on the implementation specifics, tests should focus on the intended result.

If you use conditions like if, while, switch, for, and so on, your tests will become less predictable and readable. If it appears that including logic in a test is unavoidable, divide it into two or more tests.

• Avoid test interdependencies

Interdependencies between tests make them unstable and challenging to perform and debug. Test runners typically run numerous unit tests simultaneously without regard for order. To eliminate test interdependencies, each test case should have its own setup and takedown procedure.

How to perform Unit Testing with Selenium

This section highlights a few widely used unit testing frameworks for popular programming languages, like Java, Python, JavaScript, Ruby, etc., that integrate easily with Selenium.

You can run these automated tests using BrowserStack Automate platform. BrowserStack allows you to test your website and application on 3000+ devices seamlessly. Besides this, developers have the freedom to choose any language and run tests in real user conditions. Once seamlessly integrated, use the following:

• Run Selenium Webdriver tests with JUnit
• Selenium and NUnit Framework
• JUnit Testing Framework: Get Started for Automation Testing with Selenium

 Here is a list of Unit Testing Frameworks in Selenium to know more.