Page 284 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Principles of Software Engineering

Notes Integration testing is a systematic technique for constructing the program true while at the same
time conducting tests to uncover errors associated with in front of. The objective is to take unit
tested components and build a program structure that has been dictated by design.
There is often a tendency to attempt no incremental integration; that is, to structure the program
using a “big bang” approaches. All components are advance. The entire program is tested as a
whole. And chaos usually results of errors is encountered. Correction is difficult because isolation
of causes is placated by the vast expanse of the entire program. Once these errors are new ones
appear and the process continues in a seemingly endless loop.
Top-down Integration
Top-down integration testing is an incremental approach to construction of structure. Modules
are integrated by moving downward through the control hierarchy, beginning with the main
control module (main program). Modules subordinate (and ultimately subordinate) to the main
control module are incorporated’ structure in either a depth-first or breadth-first manner.
Depth-first integration would integrate all components on major control path of the structure.
Selection of a major path is somewhat arbitrary and depends on application-specific characteristics.
For example, selecting the hand path, components M , M , M would be integrated first. Next,
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M or (if necessary for proper functioning of M ) M would be integrated. Then, the central and
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right hand control paths are built. Breadth-first integration incorporates all components directly
subordinate at each level, moving across the structure horizontally. From the figure, components
M , M , and M (a replacement for stub S ) would be integrated first. The next control level, M ,
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M , and so on, follows.
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The integration process is performed in a series of five steps:
1. The main control module is used as a test driver and stubs are substituted for all components
directly subordinate to the main control module.
2. Depending on the integration approach selected (i.e., depth or breadth first), subordinate
stubs are replaced one at a time with actual components.
3. Tests are conducted as each component is integrated.
4. On completion of each set of tests, another stub is replaced with the real component.
5. Regression testing may be conducted to ensure that new errors have not been introduced.

Figure 14.1: Top-down Integration

M1

M3
M2

M4 M5

M6 M7

(a)

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