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8.1 Development testing 217

Test Cases

A B

C
Figure 8.7 Interface
testing

2. Shared memory interfaces These are interfaces in which a block of memory is
shared between components. Data is placed in the memory by one subsystem
and retrieved from there by other sub-systems. This type of interface is often
used in embedded systems, where sensors create data that is retrieved and
processed by other system components.

3. Procedural interfaces These are interfaces in which one component encapsu-
lates a set of procedures that can be called by other components. Objects and
reusable components have this form of interface.
4. Message passing interfaces These are interfaces in which one component
requests a service from another component by passing a message to it. A return
message includes the results of executing the service. Some object-oriented sys-
tems have this form of interface, as do client–server systems.

Interface errors are one of the most common forms of error in complex systems
(Lutz, 1993). These errors fall into three classes:

Interface misuse A calling component calls some other component and makes an
error in the use of its interface. This type of error is common with parameter inter-
faces, where parameters may be of the wrong type or be passed in the wrong
order, or the wrong number of parameters may be passed.
Interface misunderstanding A calling component misunderstands the specifica-
tion of the interface of the called component and makes assumptions about its
behavior. The called component does not behave as expected which then causes
unexpected behavior in the calling component. For example, a binary search
method may be called with a parameter that is an unordered array. The search
would then fail.
Timing errors These occur in real-time systems that use a shared memory or a
message-passing interface. The producer of data and the consumer of data may