Boundary Value Generator

Generate the 6 canonical boundary test cases for any numeric, date, string-length, or decimal input.

Runs 100% client-side
Copy outputCSV & Markdown export
On this page4 sections

Enter a type, min, and max then click Generate to see the 6 boundary test cases.

HOW TO USE

  1. 01Pick the input type — Number, String length, Date, or Decimal — to match the field you're testing.
  2. 02Enter the minimum and maximum allowed values for that field.
  3. 03Click Generate to produce the six boundary values (min−1, min, min+1, max−1, max, max+1).
  4. 04Copy the table or Download CSV to drop the cases straight into your test suite.

Try it

Age gate: Type = Number, Min = 18, Max = 120 → Generate

WHEN TO USE

Use Boundary Value Analysis (BVA) whenever an input field operates within a defined range. BVA generates the six values most likely to expose off-by-one bugs -- one below the minimum, the minimum itself, one above the minimum, one below the maximum, the maximum itself, and one above the maximum. Use it for numeric fields, date ranges, string length limits, and decimal precision fields.

WHAT BUGS THIS FINDS

  • Off-by-one errors

    Developer used < instead of <=, so the boundary value itself is incorrectly rejected.

  • Fence-post bugs

    Boundary treated as out-of-range when it should be included -- classic integer miscount.

  • Decimal rounding

    Fields that appear correct at integer boundaries but silently truncate at decimal precision.

  • Date/time edge cases

    Midnight, end-of-day, leap-year Feb 28/29, and DST transitions treated as out-of-range.

QA USE CASES

01

User registration age gate

Min 18, Max 120 → test 17, 18, 19, 119, 120, 121

02

Credit card CVV (3-digit)

Min 0, Max 999 → test -1, 0, 1, 998, 999, 1000

03

File upload size limit (10 MB)

Test 0 B, 1 B, 9.99 MB, 10.00 MB, 10.01 MB

04

Promo code discount (%)

Min 1, Max 100 → test 0, 1, 2, 99, 100, 101

05

Username length (3-20 chars)

Test 2, 3, 4, 19, 20, 21 character strings