Qualitative testing of an application determines its reliability. Testing is an integral part of the development cycle, but there is no easy way to do quality testing “in one step”. Each product goes through a series of tests, both from the developers and the QA department, to evaluate how the application performs in different situations.

Unit testing and integration testing are among the two most commonly used types of testing that software is subjected to.

So let’s see what these tests are, how they differ and from what point of view they help to make software better.

Unit Testing

Reliable software is the one that the developers themselves have tested by checking the code of the written modules. Unit testing, also called unit testing, tests one unit from an application (down to a single function or method).

To better understand unit testing, let’s imagine the source code for a large, complex application. Developers write the code and think through the logic of the application, and they must also give the very first answer whether their software is functional, secure, productive enough. Thus, a unit test tests a module in isolation from other code in the project.

Although unit tests are usually simple, they rely heavily on the initial orderliness and “clarity” of the code. Small, well-structured code, “not too coherent” code (no many links to other modules) – easy to test. This allows you to catch errors at the initial stage, and not at the very end, when the price of fixing an error rises.

Unit Testing Challenges

Such testing is, in principle, the most common and simplest type of testing (perhaps the very first in existence), performed by the same people who wrote the code for all components and functions. This drastically simplifies testing. But if unit tests force testers to do, then challenges are possible here. Especially if the code was written without regard to unit testing.

Pros of Unit Testing

Modules are tested in isolation, which gives a good result in the form of tested code, right at the beginning of the pipeline

  • Fast proven methodology
  • Tested by those who wrote the code
  • Fast execution of tests, so you can test many times
  • Reduced technical debt and maintenance costs on large projects

Integration testing

Unlike unit testing, which focuses on small modules, integration testing is kind of the opposite – it checks the entire code, plus its dependencies. Module units can be arbitrarily perfect, and the application as a whole is useless if the whole code as a whole does not work as expected in the external environment after deployment. In other words, the entire application is tested “in all its glory”.

Integration tests are performed by a QA team who execute test cases, checking the performance and functionality of the application.

Knowing that integration tests test the entire application, both its dependencies and the area of ​​interaction with external systems, it is better not to test it too many times. Although there may not be 100% test coverage, integration tests allow you to find bugs that arise from the interaction of parts of the code with each other, and such bugs are very common.

Challenges in integration testing

Although integration tests are written to test the connectivity of components in the real world, it is not always easy to create a “real world environment”. But there are good solutions for testers that bring integration tests closer to the real world.

Benefits of Integration Testing

  • Checks the “cohesion” of all code and dependencies, and how the code behaves in the production environment
  • Finds bugs both in the application code and in dependencies
  • High efficiency because interfaces and interactions between modules in the application are checked

What tests are needed, unit or integration?

Of course, situations are different. Theoretically, you need to use different types, but in reality it all depends on the requirements of the client and business goals. In general, these two types of testing should be applied sequentially. Developers “pass” their code through unit testing. Testers then do integration testing, checking the functionality and efficiency of the entire dependency application.

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