Incremental integration testing encompass the basic concepts of integration testing.  It is continuous or repetitive testing of a software application as new and fresh functionality is advised. You may need different aspects of software application’s functionality that are independent to work separately before you complete all parts of program. Programmers, software engineers, or test engineers may carry out this type of testing.

Under usual circumstances, the incremental integration testing is done whenever the software needs to have its various aspects of functionality work independently of each other. The whole functionality of the application will be combined together to complete the required software. You may also need to develop test drivers whenever it is necessary.

However, there are some essential differences between an integration test and incremental integration testing. Integration testing involves the identification of the defects of certain application as a whole. On the other hand, incremental integration testing involves identifying the defects of certain components independently from the other components.

However, the objective of both the integration testing and the incremental integration testing is quite similar. Both of them plan to determine if the different components can work together, after combination. In addition, these tests can identify the defects that were not previously seen during the unit-testing phase.

You can use several types of incremental integration tests including the commercial integration testing, the system integration testing, and the software integration testing. These incremental cycles of development will ensure that the integration testing will be conducted in an iterative manner. You should also note that it is necessary to automate integration testing, if you want regression testing to be made possible.

Integration Strategies

Integration strategy is one of the most important factors while software developers are building software applications. There are many ways to conduct integration strategy, for example, you may conduct it from bottom-up, top-down, or critical components first. It is also possible to integrate the sub-systems that are functioning first, then just put the other sub-systems later in separate phases.

Integrating a large system should entail a different strategy from integrating a small system. Most of the time, small systems are integrated in merely one phase, but it is noted that this method could be quote impractical. There are several reasons for this.

One of the major reasons is that the system might fail in various places. This would cause the debugging effort to be useless and wasteful, because it would not be able to fix all these errors. The next reason why you should not integrate an entire system in just one phase is that it would make any white box testing effort difficult, if not impossible, to conduct. This is because there is a large separation between the input data and the code modules.

Because of all these reasons, large systems must be made from several development phases that begin with the assembly of the individual modules into the low-level subsystems, later assembling these subsystems into the large subsystems. The last step will be assembling all these into the highest level of the subsystem to complete the entire system.

Incremental Integration Testing Principles

Incremental integration testing is quite tedious and the software under testing will have to be compatible with the entire testing schema. You will need to consider multiple testing phases and detect any error in each of the phase that the software application has to traverse through before you can declare it complete. Incremental integration test basically needs to be compatible with integration test and it is therefore imperative to have a solid background of integration testing techniques.

It is important to detect and fix any error at its early stages before it is integrated with the other components. These prior safety precautions will enable software developers to be in control of the entire system. If you perform only cursory glances at the integration testing in its early stages but fix the errors rigorously during completion phase then the software may not be as good you expect it to be.

Perhaps, you could have easily avoided major errors, if you had taken time to perform simple tests during the early integration phase. On the other hand, it is also impractical to perform rigorous testing in all of the development phases because of possibilities of duplication. Therefore, the suggested solution is to balance the entire integration structure, so that it can allow rigorous testing where it is necessary, while avoiding duplication at the same time.

You should also understand the relationship between integration testing and module testing as you will be combining both of them at a later stage. Before we get into that combination stage, let us look into module testing on an individual basis. In module testing, the modules are independently tested using the stubs before any integration effort is attempted. The next step is the integration testing, when the module was found to be satisfactory. In integration testing, the interactions among the modules are observed to see whether the code within the modules is correct.

Meanwhile, you can combine integration testing together with module testing. This is actually the simplest form of application for structured testing because it will form the basis to set the paths of each individual module. However, this combination is possible only when you use it for the integration subsets. In theory, the most practical testing strategy, when you combine the integration and the module methods is to test the entire application, when the entire software has been completed. However, this is impractical in real life, as this can produce lot of errors that are difficult to correct due to lack of prior testing.

Now that you have looked into both the module testing strategy and the integration testing strategy, you should know what incremental integration really is and how it fits into integration testing. There are hierarchical limits that each stage of development phases will usually encounter. You will need to set this limit to a manageable level in every stage for it to be more effective.

The hierarchical design can provide software developers will provide the effectiveness when you combine it with other related components. You should also note that when the size of the component increases, it would simplify the data set derivations. Incremental integration testing will support the hierarchal design, so that the interactions among the various components will be accurate and that redundancy will be avoided.

In practice, the basic principle of incremental integration testing is similar to a test that combines the principles of module and integration testing. To support an incremental integration test, you may want to have statements for all the modules, from one another, so that you can use them during the integration. However, if you want to make a flexible testing criterion, then you should make each statement to execute right during the early phase of the development.

The early phase may consist of just the first phase within a single module or the entire software. In fact, the hierarchal design in integration testing is a very good model, since it has many partitioning characteristics that are cohesive and tight, but this limits the testing to only a small fraction of the entire system within every integration phase. In another way, even the structured testing come to good use to cover the general incremental integration.

The suggested solution to this problem is to use design reduction during each integration stage so that the module can provide you many reduced component graphs. However, the integration formula may not give you the exact number of independent tests for incremental integration testing. The reason could be reduced capacity to conduct cross component calls that are not a part of the entire design structure. You may not need them for the case where the result of the module that exercises another path through its caller. In effect, an incremental integration test uses the structured testing approach to be more effective.

Conclusion

Incremental integration test is one of the common methods used for the integration testing approach. Nevertheless, it is still an important part of the overall integration approach because it uses the basic principles of structured testing which eventually renders it very effective and accurate. In the end, even integration testing consists of several categories that includes incremental integration testing as well.

Incremental integration test has its share of merits and demerits too. It depends on the software that is under development. Some applications may never need this testing. If you feel that the software that you are testing undergo integration testing during the developmental phase, then you can skip incremental integration testing phase and proceed to other tests that might enhance the stability and efficiency of the application. However, incremental integration testing is still one of the most formidable tests that can create a solid and robust software application.