Integration testing and end-to-end testing in software development – all steps explained
Both integration tests and end-to-end tests (E2E testing) are an essential part of professional software and app development. While integration tests focus on testing the interaction of different components or modules, end-to-end tests simulate the entire user journey through an application to ensure that all requirements are met.
Why are integration tests and E2E tests particularly important in app development?
Integration tests and E2E tests are particularly important when complex software architectures interact with external services. This is very common with apps. Database integrations, or the integration of external applications such as Salesforce, Microsoft Dynamics, or increasingly AI systems, are standard in many apps (development of apps with artificial intelligence).
In such cases, integration tests ensure that data flows function smoothly, APIs interact correctly, and no unexpected errors occur when using the app.
What is tested with integration tests?
As mentioned at the beginning, integration tests check the smooth interaction of all software components. Specifically, this includes:
Interface compatibility: Tests are carried out to determine whether individual software modules can communicate with each other.
Data flow control: It is validated whether data is transferred, processed, and stored between different modules as planned.
Identification of potential sources of error: An important step is the identification of potential software errors – especially in the case of inputs and usage patterns that are not necessarily standard.
Performance and stability: Testing system stability during cross-module operations and under high load. Particularly important for apps: Applications must still run flawlessly on older smartphones and operating systems.
Which end-to-end testing frameworks are well suited for automated testing?
Since end-to-end tests check applications from start to finish by simulating real user interactions, they are easy to simulate. While this does not replace manual QA, it helps save time and resources while ensuring that no features or usage scenarios are overlooked.
In our blog post on end-to-end testing frameworks, we compared the advantages and disadvantages of the most widely used testing frameworks.
In 6 steps: How are software integration tests structured?
The development and execution of integration tests follows a clearly structured process that usually consists of the following six steps:
Planning the test strategy
Defining test objectives, procedures, and environments.
Creation of test cases
Development of realistic user scenarios. These are based on the requirements and interface specifications of an application.
Set up test environment
Establishment of suitable infrastructure. In the case of apps, this is usually done on a cloud basis.
Conducting the test
Use of tools and automation solutions to perform tests efficiently (more on tools in the next section).
Evaluation and documentation
Analysis of test results, logging of errors, and detailed reports for the development team.
Continuous integration (CI)
Integration of tests into CI/CD pipelines to ensure regular and automated test cycles.
Popular approaches for incremental integration testing
There are various approaches to planning integration tests. Some of the most commonly used are:
Big Bang Integration Testing
With this approach, all components are integrated and tested at once. This is particularly suitable for small applications, such as apps with only a few external integrations and simple features. The risk of this approach is that it makes it more difficult to locate errors.
Bottom-up integration testing
The test starts with the lower, independent modules and works its way up step by step. Supported by so-called “driver” modules, this approach is particularly suitable for component-based systems.
Top-down integration testing
This approach starts with the main module and gradually integrates the underlying modules. This involves the use of “stubs” (placeholders for missing modules). Particularly suitable for systems that are highly user-oriented (this applies to most complex apps).
Mixed integration testing (sandwich approach)
The sandwich approach combines top-down and bottom-up integration testing: critical, central modules are integrated at an early stage in order to detect errors quickly and respond flexibly.
Best practices for your integration strategy
The right integration strategy is important for working cost-effectively and thoroughly. The following factors must be taken into account:
Consider integration testing early on in your software development roadmap.
If possible, it is more efficient to perform automated integration tests through continuous integration (CI/CD).
Use realistic test data and scenarios. This is the only way to achieve meaningful results.
Structured logging and detailed monitoring for error analysis must be carried out.
We recommend an iterative approach with regular test runs in order to identify all potential sources of error at an early stage and continuously improve your application.
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