Unit Test vs Integration Tests

May 16, 2022

Automated testing is an integral part of software testing. Not only does the testing catch errors and potential problems, but it helps developers ensure that their code functions as intended. However, various types of tests exist. Unit and integration tests are two of the most common, with some similarities and significant differences.

This blog post focuses on the critical aspects of unit vs integration tests. This includes what they have in common, what makes them different, and when professionals typically use them.

What Is a Unit Test?

Unit testing in programming is a process that evaluates individual source codes to establish if they are working as per the programmer’s intentions. A source code can consist of an individual class, procedure, or function.

When developing software, programmers can write unit tests before the code they’re testing is complete. Professionals refer to the process as test-driven development (TDD). Furhter, it helps ensure that the code meets the requirements set out by the tests.

Meanwhile, having a thorough unit testing process allows developers to make small changes to the code without re-running all the tests. Developers can also find errors and defects before any code is ready for integration testing.

While unit testing enables developers to assess the quality of their code, they can run it frequently to provide immediate feedback on code changes. It’s important to note that developers should isolate unit tests from other software units to prevent unexpected interactions between test units and code changes.

When done correctly, unit tests can serve as documentation for the functionality of a particular piece of code. This provides the programmer with confidence in proceeding with the development process in the long run.

What Is an Integration Test?

Software developers using a unit test instead of integration tests for individual source codes.
Software developers testing individual source codes.

On the other hand, automated integration testing is a set of tests designed to evaluate the interactions between multiple code modules or systems. It’s generally considered more complex than unit testing since it typically involves numerous units interacting.

The goal of integration testing is to ensure that components in an application interact with each other as expected. It helps developers identify any defects or inconsistencies that might exist in the software’s design, architecture, or implementation.

Integration testing is typically performed after completing the unit tests, and it tends to be more focused on functionality than individual classes or code modules.

Unit Test vs Integration Tests

When comparing unit tests vs integration tests, we can summarize by discussing the key similarities and differences. Doing that will enable you to distinguish when to adopt each testing type.

What’s the Same

Both unit tests and integration tests are considered to be automated. Therefore, it means that the testing is performed by software rather than a human, which can significantly help speed up the testing process.

Unit and integration tests fall under programming, which requires coding in a specific language to create the test. In both cases, a need exists for a testing framework that executes the tests and provides feedback.

In addition, both tests run on the same machines or devices. It allows for easier comparison or reporting of test results between them.

What’s Different

While there are some similarities between unit and integration tests, they also have some key differences. They include:

  • The most significant difference is that unit tests tend to be more granular, focusing on assessing specific interactions with external dependencies like databases, IO, or networks. On the other hand, integration testing is generally broader and can cover multiple units in an application. In addition, integration testing addresses system-level concerns, including resiliency, performance, or scalability.
  • Another key difference is that unit tests are typically run as part of TDD – a process where developers write unit tests before creating any code. Meanwhile, the running of integration tests comes after performing the unit tests and when the code is ready for testing.
  • The development team executes unit testing, while a separate QA team often does integration testing.
  • While it is much easier to establish the errors in unit testing, integration testing may involve multiple software components, which means the results are not straightforward.
  • Developers using unit testing will first carry out module specifications, while in integration testing, they will have to start with interface specifications.

When to Use a Unit Test vs Integration Tests

To better understand when to use unit tests and integration tests, a Test Pyramid concept must come into play. It’s an approach that highlights the knowledge of when you should prioritize fast unit tests over slower testing. Although the concept is ambiguous, it is a guide developers can use to create a testing strategy.

The unit tests are at the bottom of the pyramid, which should make up the vast majority of your test suite. They’re typically fast and easy to write, making them ideal for frequently running during development. As you move up the pyramid, tests become slower and more challenging to write but can provide more comprehensive coverage.

The next level is integration tests. These generally take longer to run than unit tests but can provide valuable insights into how different system parts work together. These tests run less frequently than unit tests, but remain an essential part of development.

At the top of the pyramid are end-to-end tests and UI tests, which involve running your entire application against a real environment and taking hours or even days to complete. These tests are typically challenging to write and may require a lot of configuration for each test run. However, they provide valuable insights into how well your application will perform in production.

The Test Pyramid is a helpful guide, but it’s important to remember that there are no hard and fast rules for unit tests and integration tests. Every project is different. Thus, you may need to adjust your testing strategy based on the specific needs of your project.

Learn More About Unit Test vs Integration Tests

Unit and integration tests are two essential tests you should include in every software development project. They each have their strengths and weaknesses, and they should run together to provide comprehensive coverage of an application.

Knowing when to use each type of test is essential for a smooth, efficient workflow. If you’re looking for more information on unit testing, we have a comprehensive unit test guide that can walk you through everything you need to know.