A selection technique in which test data are chosen to lie along "boundaries" of the input domain [or output range] classes, data structures, procedure parameters, etc. Choices often include maximum, minimum, and trivial values or parameters. This technique is often called stress testing.

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A test data selection technique in which values are chosen to lie along data extremes. Boundary values include maximum, mini-mum, just inside/outside boundaries, typical values, and error values.