L17 Integration Testing

Summary

This tutorial by Phil Copeman delves into integration testing, emphasizing its importance post-unit testing to ensure components work harmoniously as per high-level design. It focuses on testing component interfaces and interactions, avoiding common pitfalls like skipping to system testing or lacking traceability. The tutorial illustrates the process with a vending machine example, highlighting the need to check not just the final output but the entire sequence of actions. It also discusses the role of message dictionaries in automotive diagnostics, emphasizing the necessity of testing various message types and values to validate system behavior against design specifications.

Takeaways

• 🔍 Integration testing is conducted after unit testing to see how various pieces of the system work together.
• 🏗️ It traces back to the architectural and high-level design work, ensuring components not only function internally but also interact as intended.
• 🔄 The primary focus of integration testing is on the interfaces between components, assessing if they handle input sequences and interactions correctly.
• 📈 Integration testing aims to confirm that modules align with the high-level design, especially in terms of sequence diagrams.
• 🔄 Avoid the anti-pattern of skipping straight to system testing after unit tests, as this might miss subtle interaction issues.
• 🔗 Ensure traceability from integration tests to the high-level design to maintain the connection between testing and design intent.
• 🚫 Integration tests should not be pass/fail based on system function alone but should focus on the correctness of interfaces and interactions.
• 🛠️ A simple integration test example involves a vending machine sequence diagram, where the test checks if the system correctly processes a coin insertion and subsequent actions.
• 📊 Integration testing should cover all sequence diagrams, testing nominal behaviors, missing inputs, false preconditions, and invalid sequencing.
• 📝 High-level designs often include interface descriptions, such as message dictionaries, which should be tested for message structure, field values, and exception handling.
• 🔑 Best practices in integration testing emphasize the importance of tracing tests to the high-level design and covering all interactions to ensure the system works as intended.

Q & A

What is the primary purpose of integration testing?

The primary purpose of integration testing is to ensure that the various pieces of a software system work together as intended after individual components have been unit tested. It focuses on the interactions between components and their adherence to the high-level design.

Why is it important to conduct integration testing after unit testing?

Integration testing is important because unit testing alone cannot identify interaction problems between components. It ensures that the components, which have been individually tested, function correctly when combined and that the overall system matches the high-level design.

What are the potential anti-patterns or pitfalls of integration testing mentioned in the script?

The script mentions three anti-patterns: skipping straight to system testing after unit testing without conducting integration tests, lacking traceability from integration tests to the high-level design, and basing integration test pass criteria on system functionality rather than on the proper functioning of interfaces.

How does integration testing relate to high-level design?

Integration testing is intended to verify that the modules of a system match the high-level design, particularly focusing on the sequence diagrams and ensuring that the system behaves as the design specifies.

What is a sequence diagram and how does it relate to integration testing?

A sequence diagram is a type of diagram in the high-level design that shows the interactions between objects or components in a system over time. Integration testing uses these diagrams to check that all inputs result in correct outputs and that every component interface is exercised as expected.

What should be the focus of an integration test for a vending machine as described in the script?

The focus of an integration test for a vending machine should be to exercise a specific sequence diagram, ensuring that all inputs lead to correct outputs, every component interface is tested with relevant values, and the sequence of actions matches the expected behavior as per the high-level design.

Why is it incorrect to base the pass/fail criteria of an integration test solely on the final output?

Basing the pass/fail criteria solely on the final output is incorrect because it overlooks the importance of the intermediate results and the sequence of actions. Integration testing should verify that all arcs appear in the expected sequence and that all side effects and timings happen as expected according to the high-level design.

What is an example of an interface description used in integration testing?

An example of an interface description is the OBD2 parameter ID message dictionary, which defines automotive operational parameters and their associated data structures or fields in network packets, allowing for the testing of message structures, values, and exception handling.

How should integration testing be approached in terms of best practices?

Integration testing best practices involve focusing on the interaction of components, tracing tests to the high-level design, exercising all arcs on every sequence diagram, and covering all modules, network interfaces, message types, and data fields to ensure the system works as intended.

What are the two main pitfalls of relying solely on system testing instead of conducting integration testing?

The two main pitfalls are missing system integration edge cases where the system may appear to work but the internal logic is incorrect, and the difficulty of exercising off-nominal sequence diagrams at a system level, which can lead to overlooking specific situations that the system will not handle as intended.

Why is traceability from integration tests to the high-level design important?

Traceability is important because it ensures that the integration tests are based on a clear reference point, allowing testers to verify whether the system is behaving as the high-level design specifies. Without traceability, there is no way to know if the system is functioning as intended.