Integration Testing – Procedure and Purpose

Date: 05-12-2023

Integration testing is a critical software testing process that verifies the interactions and data exchange between different software components. Integration testing identifies any integration issues or bugs when different elements are merged or interact and resolves them early in the development cycle.

Integration testing can be done by selecting modules individually, following a proper sequence. This method ensures that all integration scenarios are covered and no significant defects are missed. Integration testing helps to identify faults in the interaction between integrated units and the interaction time between the integrated units.

Integration test approaches

The following are types of integration testing approaches:

Big-Bang Integration Testing 

Integration testing is a vital aspect of software development that ensures that all modules of a system work cohesively. One approach to integration testing is big-bang integration testing, which involves the simultaneous testing of all modules of a software application. This approach suits systems with low interdependence between modules or when individual component testing is not feasible. 

However, big-bang integration testing has its limitations. For instance, identifying errors during testing can be challenging, given the high complexities and numerous interactions between modules. Additionally, debugging errors can be a costly and time-consuming process. Despite its potential risks, big-bang integration testing remains essential for verifying system functionality and detecting integration issues early in the development cycle.

Advantages

• It’s convenient for small systems.
• The approach is straightforward.
• It can be completed quickly without needing much planning or coordination.
• It may work well for small systems or projects with few interdependent parts.

Disadvantages

• There’s a lot of delay waiting for all the modules to be integrated.
• High-risk critical modules aren’t isolated and tested first because all modules are tested at once.
• It’s not good for long projects.
• There’s a high risk of integration issues that are hard to identify and diagnose.
• This can result in long, complex efforts to debug and troubleshoot.
• It can cause system downtime and increase development costs.
• It may not provide enough visibility into the interactions and data exchange between parts.
• This may lead to a lack of confidence in the system’s stability and reliability.
• It can cause decreased efficiency and productivity.
• It may cause a lack of confidence in the development team.
• It can result in system failure and decreased user satisfaction.

Bottom-Up Integration Testing

Bottom-up testing is a process where each lower-level module is tested with higher-level modules until all modules are tested. This type of integration testing ensures that the interfaces among various modules within each subsystem are thoroughly tested. Test drivers are used to perform this testing to drive and pass appropriate data to the lower-level modules.

Benefits

• No stubs are required
• Multiple disjoint subsystems can be tested simultaneously
• It is easy to create test conditions
• It suits best for applications that use a bottom-up design approach
• It is easy to observe test results.

Drawbacks

• Driver modules must be produced 
• The complexity can increase when the system is made up of a large number of small subsystems. 
• A working model cannot be represented until all the modules have been created.

Top-Down Integration Testing 

The top-down integration testing technique aims to simulate the behavior of low-level modules that are not yet integrated. Testing is conducted from the top to the bottom, starting with high-level modules before moving on to low-level modules and finally integrating the low-level modules into the high-level to ensure the system functions as expected.

Advantages

• Ability to debug modules separately
• Need for few or no drivers
• Greater stability and accuracy at the aggregate level
• It enables easier isolation of interface errors
• Identification of design defects at early stages

Disadvantages

• The need for many stubs
• Inadequate testing of lower-level modules
• Difficulty in observing test output
• The challenge of stubbing design

Mixed Integration Testing

Mixed integration testing, also known as sandwiched integration testing, is a testing approach that combines both top-down and bottom-up testing methods. In the top-down approach, testing commences only after the top-level module has been coded and unit-tested. Similarly, in the bottom-up approach, testing begins only after the bottom-level modules are ready. The sandwich or mixed approach overcomes the shortcomings of top-down and bottom-up methods and is also called the hybrid integration testing method. Stubs and drivers are also used in mixed integration testing.

Advantages 

• A mixed approach is useful for large projects that have several sub-projects. 
• This sandwich approach allows for parallel testing in the top and bottom layer tests.

Disadvantages 

• It can be quite expensive, as one part of the process follows a top-down approach while the other follows a bottom-up approach. 
• This testing type is not suitable for smaller systems with significant interdependence between different modules.

Applications

To ensure the successful integration of an application, it is crucial to follow a well-defined process. These steps can help achieve this objective:

Component Identification

Identify all the individual components of your application that need to be integrated, including any third-party services, frontend, backend, and database.

Test Plan Development

Develop a thorough test plan covering all possible scenarios and test cases required to validate the integration points between different components. This plan should encompass testing various aspects such as data flow, communication protocols, and error handling.

Test Environment Setup

Creating a test environment that closely resembles the production environment could significantly increase the accuracy and reliability of the outcomes of your integration tests. Therefore, it is essential to ensure that the test environment setup is comprehensive and precise.

Test Execution

Start with the most important and complex tests, and log any issues or defects you come across during testing.

Results Analysis

Analyze the results of your integration tests to identify any defects or issues that need to be addressed. This may involve working with developers to fix bugs or change the application architecture.

Repeat Testing

Once defects have been fixed, repeat the integration testing process to ensure the changes have succeeded and the application works as expected.

Following these steps will help to ensure a successful application integration process.

Read Also: What is Unit Testing? Its Importance in Software Testing