How do you decide what to test in unit testing versus other types of testing?

Unit testing is a fundamental practice in software testing that involves verifying the functionality of individual components or units of code. But how do you decide what to test in unit testing versus other types of testing, such as integration testing, system testing, or acceptance testing? In this article, you will learn some criteria and guidelines to help you make this decision and improve the quality and efficiency of your testing process.

1 The purpose of unit testing

Unit testing aims to isolate and test the smallest possible units of code, such as functions, methods, classes, or modules, and ensure that they work as expected. Unit testing helps you detect and fix bugs early, refactor and optimize your code, document your design and logic, and simplify the integration of different components. Unit testing also enables you to use test automation tools and frameworks, such as JUnit, NUnit, PyTest, or Mocha, to run your tests quickly and repeatedly.

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Zouhair B.

Champion Senior QA Engineer | Selenium & Robot Framework Master Trainer | ISTQB® (CTFL) | ISTQB® Agile Tester (CTFL-AT) | A4Q® Selenium Tester | Jira Xray | Scrum Fundamentals SFPC™ Certified
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La décision quant à ce qu'il convient de tester dans les tests unitaires par rapport à d'autres types de tests dépend de plusieurs facteurs. Les tests unitaires se concentrent sur la vérification des composants individuels, tels que les fonctions ou méthodes, pour assurer leur bon fonctionnement. Les tests d'intégration examinent comment ces unités interagissent, identifiant les problèmes d'interfaces. Les tests de système évaluent le système dans son ensemble, tandis que les tests de non-régression assurent la stabilité après des modifications. Les tests d'acceptation garantissent que le système répond aux besoins de l'utilisateur.

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Ayush Srivastava

SDET @UST | Ex - UKG, Capgemini
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Unit testing aims to test the software components individually, like modules, functions, classes, etc. They cover the small scope of testing to validate their functionality. Unit testing aims to validate each piece of code functionality as an individual. They are often written by developers to cover various scenarios. Other types of Testing- Integration testing: It focuses on the integration of different components of software to ensure they are working together. System Testing: It focuses on testing the entire system as a whole, to ensure the end-to-end functionality is working fine. Acceptance testing: It focuses on testing from the user's point of view. Non-functional testing: It focuses on performance, security and another testing.

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Dhairya N. Shukla

Quality Assurance Team Lead | Software Testing Professional | Ex-KiwiQA | Ex-elink | ISTQB® CTFL
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- Unit Testing : Focuses on testing individual units or components of code in isolation. and for that,Verify that each unit of code works as intended at the smallest level. Test Individual functions/methods, Isolated code units without dependencies, Edge cases, boundary conditions, normal scenarios, Exceptional cases and error handling - Other testings : Functional, Integration, System, UAT, Regression, Performance and Security. Other testing ensures a balanced approach to testing, with a focus on early defect detection and efficient test coverage across the entire software development lifecycle. Additionally, testing decisions should align with project requirements, timelines, and risk factors.

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2 The scope of unit testing

Unit testing covers the internal logic and behavior of your code units, but not the interactions or dependencies between them. For example, if you are testing a function that calculates the area of a circle, you would test whether it returns the correct value for different inputs, but not whether it communicates with other functions or external systems. Unit testing also does not test the user interface, the performance, the security, or the usability of your software. These aspects are covered by other types of testing, such as integration testing, system testing, or acceptance testing.

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Siddharth Vaghela

Senior Engineer at MathWorks
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Deciding the correct level of granularity at which to unit test is very important. Gone are the days where every function in every class would get its own test. Often, a certain functionality becomes the smallest atomic unit in the system that needs unit testing independently. This functionality would involve several classes and functions.

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3 The criteria for unit testing

Unit testing should follow some basic criteria to ensure its effectiveness and reliability. For example, each unit test should focus on one aspect or scenario of your code unit and have a clear and descriptive name. Additionally, each test should be able to run independently without relying on the order, state, or output of other tests. This can be achieved by using mock objects, stubs, or fakes to simulate or replace external dependencies. Furthermore, it is important to cover all the possible paths, branches, and cases of your code unit in order to test comprehensively. You can use code coverage tools to measure how much of your code is tested by your unit tests. Finally, each unit test should produce the same result every time it is run, so you should avoid using random values, dates, or inputs in your unit tests. Fixed or predefined values can be used instead, or a seed for generating random values.

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4 The benefits of unit testing

Unit testing has many advantages for developers and testers, such as improving the quality and reliability of your code, enhancing the maintainability and readability of your code, and accelerating the development and testing cycle. Unit testing allows you to find and fix bugs early, before they propagate to other parts of your software or affect users. It also helps you prevent regression bugs by giving you confidence that your changes do not break existing functionality. Moreover, unit testing helps you refactor and optimize your code while also documenting it. Finally, it can reduce the time and effort required for debugging, integration, and manual testing by automating and simplifying the testing process. Unit testing provides a common language and standard for your code which helps with collaboration and communication with other developers and testers.

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Apeksha Dalvi-Chawan

2 x LinkedIn Top Voice | Certified Scrum Master | Scrum Master Mentor & Co-Trainer | Jira & Confluence Expert | Agile Practitioner | Software Testing Coach & Consultant | QTP Certified | ISTQB CTFL®
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Based on my experience, unit testing proves advantageous for both developers and testers. When developers execute comprehensive unit tests, it guarantees a streamlined smoke testing phase, where the build is not rejected based on fundamental feature functionality, enabling testers to focus more effectively on other types of testing.

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5 The challenges of unit testing

Unit testing can be a challenge, such as writing good unit tests which may require learning new tools and frameworks, and designing and structuring tests well. Additionally, there is a cost associated with unit testing in terms of resources like time, money, and people. It is important to balance the trade-off between the quality and quantity of your unit tests, and prioritize the most critical parts of your code. Moreover, unit testing alone is not enough to ensure the quality and functionality of your software, as integration testing, system testing, or acceptance testing should also be performed to test interactions, dependencies, and requirements. It is essential to coordinate and align your unit testing with these other types of testing to ensure they complement and support each other.

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Balagopal Prakash Kumar

Senior Function Developer | Energy Storage Systems Expert| Model Based Development | Control Engineer
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Spot on! Testing edge cases is like exploring uncharted territories. It's not just about finding needles in haystacks; it's about predicting where those needles might hide. Pro tip: Keep a treasure map of edge cases to navigate this testing adventure.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How do you decide what to test in unit testing versus other types of testing?

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1 The purpose of unit testing

2 The scope of unit testing

3 The criteria for unit testing

4 The benefits of unit testing

5 The challenges of unit testing

6 Here’s what else to consider

Software Testing

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How do you decide what to test in unit testing versus other types of testing?

1

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3

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5

6

1 The purpose of unit testing

2 The scope of unit testing

3 The criteria for unit testing

4 The benefits of unit testing

5 The challenges of unit testing

6 Here’s what else to consider

Software Testing

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