Multiple forms of testing, both manual and automated, can ensure quality control and determine how well the software performs. One such type, integration testing, is sometimes lumped in with other types of tests.
But, integration testing happens at a specific part of a development project, and it has a very particular purpose. But what is it, exactly?
Integration testing is the testing of various modules of the software under development together as a group. This determines whether or not they function together seamlessly as part of the system or whole.
Some confuse it with unit testing, which also tests parts of the whole, but the difference is when you perform the test and how you carry it out.
Unit testing is done on modules or units of the project individually to make sure they function as they should. Integration testing is done on groups of these modules to make sure they work together and interact properly. While unit testing is one of the earliest tests performed in a project, integration testing is usually done later in the project timeline.
Below, we'll take a closer look at integration testing, why it's important, best practices for integration testing, integration testing tools, and more.
Why is integration testing important?
No matter how well you write code, the potential for bugs, vulnerabilities, and errors to occur will always exist. This is more likely when multiple programmers work together and collaborate on a single project.
Each will use their own logic and problem-solving methods, despite the plans and strategies created by the development team. So, integration testing has multiple benefits in this environment, including:
- Successful integration of modules. Most projects are big enough that development is broken down into numerous parts or modules. Integration testing verifies that all the parts communicate well and work together to achieve the purpose of the software.
- Data integrity. When programmers move from one module to another in development, there's always the risk of losing or inadvertently changing pieces of data. Integration testing can be used as a form of regression testing to verify that no inadvertent changes or corruptions have taken place.
- User-based scenarios. One of the most important reasons to conduct integration tests is to create critical user-based scenarios and make sure they play out correctly. Individual components of the software will need to communicate properly when grouped, adapting and responding to multiple possible results.
- Third-party testing. Integration testing also verifies that groups of modules or units of coding interact properly with Application Programming Interface (API) tools. This lays the foundation for acceptance testing toward the end of the project, ensuring a user-friendly end product.
Criteria and best practices for integration testing
Since integration testing has a specific purpose and place within the overall software testing strategy, what are the requirements for running integration tests?
- The team should create a test plan to determine the type of test and the desired results.
- Test cases need to be prepared and testing data created.
- Unit testing must have been completed already (this is perhaps the most important criteria).
- Any of the defects exposed by unit testing must be resolved.
- A test environment needs to be set up.
Some examples of the test cases you could run to verify that components work together to achieve the desired result might be:
- The checkout process on an e-Commerce site.
- The login process on a site where users enter credentials.
- Message notifications and their respective redirect links.
Types of integration tests
In general, there are two types of integration testing: The Big Bang Approach and The Incremental Approach.
The Big Bang Approach
As the name suggests, in this type of test, all the units or modules are grouped together and tested as a whole.
- Works best for small systems.
- Yields quick results.
- Greater difficulty in locating faults.
- Potential for overlooking a component.
- All units need to be complete, so testing can't begin early.
- High-risk modules don't get specialized attention.
The Incremental Approach
Rather than grouping and testing all the modules at once, incremental testing tests the integration or interaction of a few units at a time. There are two basic methods for this: "Bottom-Up" and "Top-Down."
In this approach, lower-level modules are integrated and tested first. The results lay the foundation for higher-level testing later.
- Locating and fixing faults is easier.
- No need to wait for all units to be completed before testing begins.
- Critical, high-level components are tested last.
- Not possible to create an early prototype.
This approach is the opposite of the bottom-up approach. High-level modules are integrated and tested first, and then low-level modules are tested and then integrated as their functionality is verified.
- Locating and fixing faults is easier.
- It's possible to create an early prototype.
- Tests performed based on priority reveal major flaws you can fix before complete integration.
- Stubs have to be created for missing modules.
- Lower-level units are often inadequately tested.
A third approach that combines the best of these two approaches is called Sandwich Testing or Hybrid Integrated Testing.
Tools for integration testing
Tools for integration testing can be categorized as follows:
Popular programming-language specific
These are tools used for rarer languages or languages with fewer tests available. An example is GoConvey for Golang. You can begin programming with Go by enrolling in our online course for learning Go.
Careers using integration testing
Professionals of all kinds either conduct integration tests or use their results for their job, including:
- Business Analysts
- Quality Analysts
- Software Engineers
We can quickly equip you with the skills you need to start or further a career in various tech positions. To start learning some of the programming languages used in software development and testing, check out courses like: