Using boundary value analysis
Within a partition, not all values are equally important. Bugs are much more likely on the boundaries of partitions where off-by-one errors may be present, for instance, if greater-than-or-equals is used instead of equals. The idea is simple enough: when there is a boundary, you need to test the values just lower and higher to ensure the divide is in the right place.
As with equivalence partitions, boundaries might be explicitly listed within the specifications or they may be implicit aspects of how a feature was implemented. Examples of explicit boundaries are:
- Tax rates: The values up to X thousand are taxed at one rate, and values from X to Y thousand are taxed at another
- Ages: Users below 13 are banned, users between 13 and 18 get a child account, and users over 18 get an adult account
- Passwords: The length of passwords must be over eight characters
Examples of implicit boundaries will depend on your product’s implementation...
