Integration Testing vs Unit Testing: Which One to Use?

While performing testing for your software development, you might choose the automated option. There are two automated testing types in software development: one is integration testing and the other one is unit testing. However, not everyone knows about integration testing, and that’s why people use unit testing more often. Also, with unit testing, you can test the infrastructure and the codes within the software. But with an integration test, you can determine if your software is functional and can be ready for launch. Even though integration testing and unit testing are similar, they come with differences. Here, we will demonstrate how integration testing and unit testing help you create a functional app in their ways.

What is Unit Testing? 

The developer determines whether a small unit or codebase behaves the way the designer planned in the unit test. These codebases are isolated, and a single unit test is called a “test case” that includes sections of codes that exert the production code and then verify if the result matches the expected outcome. Therefore, the unit test does not exert the user interface but communicates with the underlying API. There are manual and automated software development tests, and the unit test is unique. Developers are the ones who write and read the codes in unit testing, but it does not have the purpose of serving the final user, unlike any other testing. Instead, a unit test helps the developers determine if the work they produced is what they intended. After performing a series of unit tests, the developers code the software more efficiently as they are now confident that the unit test will show the proper results.

What Are the Rules of Unit Tests?

Unit tests use codes to verify the performance of the software, and in these tests, the developers are the main consumers, unlike other types of tests. But to learn the difference between unit tests and integration tests, you will have first to know the rules of unit tests. Here is the brief of what we are saying:

• A unit test is not a unit test if it communicates with the database.

• A unit test should not interact across the network.

• It should not interrupt the file system.

• A unit test won’t be run with other types of performance testing. 

• To run a unit test, you will have to edit the configuration file on your production and testing environment.

For a developer to run a unit test, he must isolate the codebase first. And then, he will have to run a unit test while not engaging in any other types of tasks in the background. 

What is the Importance of Isolation in Unit Tests?

The main focus of the unit test is to quicken the testing process, but if it interacts with the database or file system, it will slow down the process. However, there is a tricky thing about unit tests you must know. When a unit test is failing, it will not come back to start working until you change the source code. Similarly, when a test is running perfectly, it should not fail if you haven’t done any changes to its codebase. If a test depends on other tests or external elements, it can change its status for other reasons that don’t include the changes in the code. And when it comes to giving feedback, a unit test will cover only a certain tiny section of the code. If the test fails, you can be assured that the issue happened in that specific section of the code. Therefore, if you want to get the detailed result of a code, you can use the unit test to your advantage. But if you perform a test that counts on the database or file system, you won’t be able to figure out the real source of the issue.

What is Integration Testing?

An integration test refers to a software module test that includes the modules integrated within the system. In this type of testing, the modules are tested in a group, unlike unit in unit testings. In integration testing, data communication is the main priority, and that’s why its other names are thread testing and string testing. This test is complex because every software program contains different developers’ modules. And this testing is done by two types of methods: one is the bottom down method, and the other one is a top-down method. The tester works with various modules segments from front to back and back to front to ensure that the testing process is done consistently. 

What Are the Rules of Integration Testing?

If you consider integration testing for your software development, there are some things you need to obey for a successful operation. Have a look at this section to know what we are talking about.

• Integration testing should be done before unit testing because it helps you easily find the performance issue in a particular source code after determining where the issue can be related.

• Business logic is better to be tested with unit tests than integration tests.

• Don’t run integration tests with unit tests.

• Log extensively to find out what’s causing a failure in integration testing 

• Run system tests after integration testing to stimulate your production infrastructure accurately. 

Alternatively, you can do unit testing on the software modules to determine what part of the code is faulted. And then, you can run integration testing to determine if the combination of the modules delivers a positive result. There are three approaches to integration testing that you can apply depending on your circumstance. 

The Big Bang Integration Approach, 

The Big Bang Integration, means all the modules will be grouped and tested at once. This approach is usually taken when the whole app is ready for integration tests at a specific time. However, this is not a system testing technique because, in system tests, the whole system is tested, whereas, in the BBI approach, the units and integration of modules are tested. Nevertheless, in this approach, identifying the failures becomes difficult. 

Top-Down Approach

In the top-down integration technique, the units or modules of the application are tested from top to bottom in a step-by-step process. The foremost unit will be tested separately by registering the test STUBS, and the lower units will be tested one at a time until all the units are grouped. This approach is a consistent method for testing the units/modules of the software, but the only downside of this approach is that the software’s primary functions are tested at the end.

Bottom-Up Approach

This is the reverse approach to the top-down integration method. Here, the integration tests are run from bottom to top in a step-by-step process, and then it makes sure all the modules are integrated as a singular unit. However, this approach has a disadvantage: high-level issues can only be identified after all the units are integrated.

There go all the popular integration testing approaches and how they work. Now it’s time to discover the main differences and similarities between unit testing and integration testing. 

Unit Test Vs Integration Test: Similarities and Differences 

Now that we have read the definitions and main aspects of the unit test and integration test, it’s time to summarize the different factors of both these techniques. We will demonstrate the similarities in words and then display the differences in a table to help you understand the concept thoroughly.

What Are the Similarities?

Unit and integration testing are the elements of functional testing that involve coding and developers who create the codes. And both of these tests use similar or the same tools to operate. Both testings depend on the source code for observing the performance instead of screen recording only. Developers prefer to add unit testing and integration testing to the CI/CD pipeline. But before doing so, there are also some differences you must consider.

What Are the Differences?

Conclusion: Which One Should You Choose?

To understand when to use which testing, you can use The Test Pyramid method to help you identify which tests to prioritize first. The Test Pyramid says you need to put the slow tests beneath the unit tests. For example, doing the unit test first, the integration, and E2E will maximize unit testing’s benefits. So, you will have to architect your app’s infrastructure in a way that you can isolate the code that maintains the external dependencies. Try to reduce the number of these codes so that you can start the integration testing next.