Domain Testing: Divide and Conquer - Testing Education

Myers (1979) suggested associating an equivalence class with every input
or output condition mentioned in the specification of the product under test. Myers
cited two kinds of equivalence classes associated with every input or output
condition:
1. A valid equivalence class consists of all values that serve as valid input to
the product or program under test, such that the corresponding input or
output condition is satisfied.
2. An invalid equivalence class consists of all erroneous values or invalid
inputs.
Ostrand and Balcer (1988) described the classic category partition method
of doing functional testing using specifications. The first three tasks in their method
are:
1. Analyze the specification. The tester identifies individual functional
units that can be tested separately. For each unit, the tester identifies:
• parameters of the functional unit
• characteristics of each parameter
• objects in the environment whose state could affect the
functional unit’s operation
• characteristics of each environment object
The tester then classifies these items into categories that have an effect on
the behavior of the functional unit.
2. Partition the categories into choices. The tester determines the different
significant cases that can occur within each parameter and environment
category.
3. Determine constraints among the choices. The tester decides how the
choices interact, how the occurrence of one choice can affect the existence
of another, and what special restrictions might affect any choice. (p. 679)
Kaner et al. (1999) described an example of a program whose specification
includes 64K to 256K RAM memory requirements. In this case, one could identify
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