The goal of component integration testing is to verify that the components perform as specified in an integrated environment. This environment may be component-to-component integration, component-to-hardware integration, or a combination of the two.

Though this testing category applies to two cases, the steps that one follows are similar. Therefore, the two use cases will be handled together.

These use cases are:

• Component-to-component integration: Components of a single subsystem are integrated to ensure that the they behave as designed and meet the subsystem’s requirements 
• Component-to-hardware integration: Software components integrate with the target hardware to ensure that the software interacts with the hardware as designed and meets the component’s requirements.

During Systems Analysis Design Synthesis, Systems Engineers specify the functionality of and interactions between components with activity diagrams. Individual paths through these activity diagrams may be represented as sequence diagram. These sequences specify the test cases for the component behavior and interaction.

Messages on sequences diagrams show the operation (i.e., the method) calls, the parameters using in those calls, the return values from those calls. For components within one subsystem, these calls become method calls for component-to-component integrations. For hardware interactions, these messages indicate signals sent to or received from hardware. A hardware ICD captures the interfaces between hardware and the components.