What are boundary values in testing?

Boundary values in testing are the threshold, extreme, and near-boundary input data used to verify the system's behavior at the edges of acceptable ranges.

Approaches to selecting boundary values:

• Exact boundary values: Minimum (min), maximum (max), and values very close to them (min+1, max-1).
• Values outside the boundaries: Values less than the minimum (min-1) and greater than the maximum (max+1).
• Values on and near the boundary: For open and closed intervals.

Applying the Boundary Value Analysis (BVA) testing method is effective when input data have clearly defined ranges (numbers, dates, strings of certain length).

Example: The "Age" field accepts values from 18 to 65. Boundary values for testing:

• 17 (min-1)
• 18 (min)
• 19 (min+1)
• 64 (max-1)
• 65 (max)
• 66 (max+1)

Advantages:

• High probability of detecting defects at the boundaries.
• Systematized approach to selecting test data.

Disadvantages:

• May be ineffective for non-numeric or logical input data.
• Does not replace other test design techniques.

Often used in conjunction with the Equivalence Partitioning method.