Page 186 - DCAP405_SOFTWARE_ENGINEERING

Unit 11: Testing Strategies

Good testing provides measures for all relevant factors. The importance of any particular factor Notes
varies from application to application. Any system where human lives are at stake must place
extreme emphasis on reliability and integrity. In the typical business system usability and
maintainability are the key factors, while for a one-time scientific program neither may be
significant. Our testing, to be fully effective, must be geared to measuring each relevant factor
and thus forcing quality to become tangible and visible.
Tests with the purpose of validating the product works are named clean tests, or positive tests.
The drawbacks are that it can only validate that the software works for the specified test cases.
A finite number of tests can not validate that the software works for all situations. On the
contrary, only one failed test is sufficient enough to show that the software does not work. Dirty
tests, or negative tests, refer to the tests aiming at breaking the software, or showing that it does
not work.

Task “A piece of software must have sufficient exception handling capabilities to survive
a significant level of dirty tests.“ What have you understood from this statement explain
with an example.
A testable design is a design that can be easily validated, falsified and maintained. Because
testing is a rigorous effort and requires significant time and cost, design for testability is also an
important design rule for software development.

11.1.3 History of Software Testing

The separation of debugging from testing was initially introduced by Glenford J. Myers in 1979.
Although his attention was on breakage testing (“a successful test is one that finds a bug”), it
illustrated the desire of the software engineering community to separate fundamental
development activities, such as debugging, from that of verification. Dr. Dave Gelperin and
Dr. William C. Hetzel classified in 1988 the phases and goals in software testing in the following
stages:
Until 1956 - Debugging oriented
1957-1978 - Demonstration oriented
1979-1982 - Destruction oriented

1983-1987 - Evaluation oriented
1988-2000 - Prevention oriented

Definition

Testing is not a technique for building quality systems; rather, it is a technique that is used
because we recognize that we have failed to build a fault free system. Testing assists in its repair
by identifying where the program fails to meet its specification. We will broaden the usual
definition of testing that typically refers only to the testing of code. The expanded definition
includes the testing of the many types of models, requirements, analysis, architectural and
detailed design, that are constructed in the early development phases. These models may be
represented in an executable format in a CASE tool such as BetterStateÅ or they may require a
form of symbolic execution or inspection. My justification for classifying these activities as
testing is that the inputs to one of these executions will be much more specific than the inputs to
a typical review process.

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