Unit Tests Vs. Integration Tests


By RevDeBug

When it comes to automated testing in software development, most people only consider unit tests. This makes sense, considering that unit testing is one of the most viable types of code and infrastructure testing that can also be automated.

However, the well-known unit test is not the only crucial test that’s needed to ensure that a software project’s result is a streamlined and functional one.

There’s also integration testing—which is similar to unit testing at first glance. In this article, we’re going to give you an overview of both unit testing and integration testing as well as how they differ and why they’re both necessary.

The Unit Test

Unit testing is typically an automated test that verifies each unit—or, isolated piece of coding—functions as the developer intended. 

Unit tests are conducted individually, often referred to as “test cases” consisting of segments of code that work together to perform a specific function. Each unit test evaluates the coding written to ensure that it aligns with each said function. 

However, unit tests are more structural, meaning they don’t interact with any underlying APIs. Therefore, they don’t assess the user interface or any user-end functions. 

Unlike most other types of testing, unit testing doesn’t involve the final user as the target audience, which is what makes each unit test unique. While these tests don’t focus on usability or the other non-functional aspects of an application, they still serve as genuine authentication that the user requirements are met.

The quality of unit tests depends on the ability to foresee and correctly implement cases that should be in the test suite. Common practice is to add test cases that refer to specific errors identified during production usage. It makes sense to start implementing unit tests in critical parts of the application like login, payment, etc.

Lastly, unit tests are both written and read by the developers. The entire point is to check and see if their coding works properly, document it, and to increase overall quality, reduce the cost of bug fixes and production failures. 

Ultimately, unit tests let developers know whether or not their software applications are ready to use.

The Integration Test

An integration test is essentially a software module test. It involves the modules that are logically integrated, and those modules are tested as a group versus individual units. 

Specifically, integration testing has a primary focus on data communication, which is why it’s also referred to as string testing or thread testing. Integration tests are critical considering that each software project typically consists of multiple modules that are coded by individual programmers. 

Integration is usually carried out by specific testers by two separate methods: The bottom-down method and the top-down method. In other words, each tester begins at a different segment of modules working front to back and back to front to ensure consistency

The Key Differences and Similarities

Both unit testing and integration testing are forms of functional testing that require coding and testers that are knowledgeable about said coding. Additionally, both types of testing use similar—or even the same—types of tools.

It’s also necessary to conduct both types of testing for your software application to eliminate any functional issues. 

Of course, the greatest difference between a unit test and an integration test is what exactly is being tested and how they’re tested. As mentioned earlier, unit testing involves testing individual pieces of code while integration testing involves testing modules of code to understand how they perform alone and how they interact with each other. 

Another difference between the two is the frequency with which each test should be executed. Unit testing is much easier to carry out as integration testing relies on both internal and external dependencies—or, “real” dependencies. 

Additionally, once an integration test has been set up and performed, it also needs to be thoroughly maintained. Anything left behind from a previous integration test can interfere and disrupt the next test.

The bottom line is that you can’t successfully develop a software application without conducting both a unit test and an integration test. Each test can reveal coding weaknesses that the other missed, offering developers the necessary safety net needed to move forward with other automated tests that measure different levels of their application’s functionality as well as ensuring that there are no back-end issues with the application’s infrastructure.

Both are necessary and both complement one another.

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