Boundary Value Generator

Runs in browser Test Design

Enter ranges or length limits for each field and get the complete set of boundary test values with expected outcomes.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

What are black-box test design techniques?

Black-box techniques derive test cases from the specification without reading the code: equivalence partitioning groups inputs that should behave the same, boundary value analysis tests the edges of each group (0, 1, max, max+1), decision tables enumerate combinations of conditions, state transition testing walks the allowed and forbidden state changes, and pairwise testing covers every pair of parameter values with far fewer cases than the full product.

Read the guide: How to Write Test Cases

How to use Boundary Value Generator

  1. Enter fields with min= and max= constraints (or a length limit).
  2. Choose 3-value or 2-value BVA and whether to include a nominal value.
  3. Generate to get the value table and the matching test cases.

Boundary Value Generator features

  • 3-value BVA (min−1, min, min+1, max−1, max, max+1) or 2-value BVA (min−1, min, max, max+1), plus an optional nominal mid-range value
  • Numeric ranges, decimal steps, string lengths, list sizes, file sizes and date limits
  • Valid/invalid classification and expected outcome for each value
  • Unbounded numbers get zero, negative, large and beyond-safe-integer probes
  • Numbered test cases exportable as Markdown, JSON, CSV or Gherkin

Boundary Value Generator example

3-value BVA for an age range

Input:

age: integer, min=18, max=120

Output:

Below minimum (min − 1)     17    Invalid
Minimum (min)               18    Valid
Just above minimum          19    Valid
Nominal (mid-range)         69    Valid
Just below maximum          119   Valid
Maximum (max)               120   Valid
Above maximum (max + 1)     121   Invalid

Frequently asked questions about Boundary Value Generator

What values are produced?

For every field with a range or length limit: min−1, min, min+1, a nominal mid value, max−1, max and max+1 (3-value BVA), or just min−1, min, max and max+1 in 2-value mode. The nominal mid value is an extra valid check, not a boundary: it is added in both modes while "Include nominal value" is ticked (the default). Decimals step by 0.01 and text limits are expressed in characters.

What about dates and files?

Date limits produce the day before, the boundary day and the day after; file limits produce sizes in MB around the limit; lists use item counts.

Which values should be rejected?

Only min−1 and max+1 lie outside the valid range. The table marks each value as valid or invalid together with the expected outcome.

Fields without min or max?

Unbounded numbers get zero, negative, large and beyond-safe-integer checks; other fields without limits are listed in a warning so you can add constraints.

References