Unit Testing: A Detailed Guide | BrowserStack (2024)

Home Guide Unit Testing: A Detailed Guide

By Kitakabee, Community Contributor - December 23, 2022

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.

Table of Contents

  • What is Unit Testing?
  • What is Application Unit Testing?
  • Why perform Unit Testing of Applications?
  • Unit Testing Techniques
  • Introduction to Test-Driven Development (TDD)
  • Best Practices in Unit Testing
  • How to perform Unit Testing with Selenium
  • 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.

    Read More to Learn:
    Unit testing for NodeJS using Jest Framework: Tutorial
    How to perform Unit testing for Angular apps?
    Unit testing for NodeJS using Mocha and Chai
    Unit Testing of React Apps using JEST: Tutorial
    Unit Testing in JavaScript: A Tutorial

    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.

    Also Read: What is Automated Functional Testing

    • 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.

    Read More: Difference between Functional Testing and Unit Testing

    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.

    Read More: 7 Core Best Practices in Unit Testing

    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.

    Unit Testing: A Detailed Guide | BrowserStack (2024)

    FAQs

    What is unit testing with an example? ›

    This testing is done by combining code units and verifying that the output is correct. For example, you might have a function that takes an integer as input and returns the square of that number. You would test this function by providing different numbers as input and verifying that the output is correct.

    How do you structure a unit test? ›

    As mentioned earlier, the AAA pattern (Arrange, Act, Assert) is a fundamental structure for organizing unit tests. By following this pattern, you provide clear steps that separate the setup, execution, and verification phases of the test. This separation improves the readability and maintainability of your tests.

    What are the three parts of unit test? ›

    A unit test typically features three different phases: Arrange, Act, and Assert (sometimes referred to as AAA). For a unit test to be successful, the resulting behavior in all three phases must be in line with expectations.

    What is the workflow of unit testing? ›

    Unit tests allow you to test for the correctness of the workflow definition, ensuring: Given a specific input, workflow reaches the terminal state in a COMPLETED or FAILED state. Given a specific input, the workflow executes a specific set of tasks. This is useful for testing branching and dynamic forks.

    Can unit testing be done manually? ›

    Unit tests, whether done by the software developer or quality assurance professional, are usually automated, ensuring that a section of the software meets expectations. One can also do unit testing manually. Either way, it is executed during the application or software development stage.

    What is a real life example of a unit test? ›

    An example of a real-world scenario that could be covered by a unit test is a checking that your car door can be unlocked, where you test that the door is unlocked using your car key, but it is not unlocked using your house key, garage door remote, or your neighbour's (who happen to have the same car as you) key.

    Which three items are best practices for unit tests? ›

    Arrange, Act, Assert is a common pattern when unit testing. As the name implies, it consists of three main actions: Arrange your objects, create and set them up as necessary. Act on an object.

    What is unit testing vs QA testing? ›

    While developers primarily write the unit tests, QA testers actively participate in the process to ensure comprehensive test coverage and maintain the overall quality of the codebase.

    What is the first principle of unit testing? ›

    When it comes to the properties of Unit Testing, Brett Schuchert and Tim Ottinger came up with the FIRST Principle: Fast, Independent, Repeatable, Self-Checking and Timely. Writing your Unit Tests with these properties in mind keeps your code clean. Your Unit Test has to be fast.

    What is unit testing in simple words? ›

    Unit testing is the process where you test the smallest functional unit of code. Software testing helps ensure code quality, and it's an integral part of software development. It's a software development best practice to write software as small, functional units then write a unit test for each code unit.

    What is the AAA rule in unit testing? ›

    One powerful approach to writing effective unit tests is the AAA pattern: Arrange, Act, Assert. Let's dive into it with a C# example! 🔵 Arrange: This is where we set up the test environment, create necessary objects, and define input values. In our example, we initialize a Calculator object and two integers, x and y.

    Who performs unit testing? ›

    Unit testing is a software development process in which the smallest testable parts of an application, called units, are individually scrutinized for proper operation. Software developers and sometimes QA staff complete unit tests during the development process.

    What are the stages of unit testing? ›

    It also determines whether a test case passes or fails. By following these 3 simple steps: arrange, act, and assert — we can write clean unit tests that are reliable and maintainable. It shapes our framework of mind when we wrote a test so that our tests aren't all over the place.

    How do testers do unit testing? ›

    To perform effective unit testing, testers need to understand the code they are testing. This includes understanding the purpose of the code, the expected input and output, and any dependencies or interactions with other parts of the software.

    How to do unit testing in Agile? ›

    There are two main steps to unit testing in agile. One is to write code that is testable. The other, to use suitable software to test this code. The first step, to write testable code, means that the functions you write to test the code should be clean.

    References

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