What is negative testing?
Negative testing gives a system input it should refuse — a missing field, the wrong type, a value outside its range, a malformed file, an expired token, a second click — and checks that it refuses cleanly: a specific error, no data change, no crash, nothing leaked. Positive tests prove a feature works; negative tests prove it fails safely, and edge-case tests prove it still behaves correctly under valid but unusual conditions — an exact limit, a leap day, right-to-left text, a session that expires mid-form. Those paths are where most production incidents and most security findings live. The ISTQB syllabus treats them as part of ordinary test design, not a separate discipline.
Read the guide: How to Write Test Cases
Edge caseThis tool
A valid but unusual condition
- Examples:
- A name of 60 Arabic characters; a date of birth exactly 18 years ago; a session that expires mid-form
- What the test proves:
- The feature still behaves correctly
- Generated by:
- AI Edge Case Generator: EC-01, EC-02 …
Negative scenario
Misuse or failure
- Examples:
- Bypassing validation; two conflicting updates; an expired token
- What the test proves:
- It fails safely: a specific error, no data change, no crash, nothing leaked
- Generated by:
- AI Negative Scenario Generator
How to use AI Edge Case Generator
- Describe the feature, API or form in the first box.
- List its inputs and rules in the second box — types, lengths, ranges, formats, required fields.
- Choose how many edge cases you want (3 to 40) and the output language, then press Generate.
- Use the test data column to reproduce each case, and download the list as CSV, Markdown or JSON.
AI Edge Case Generator features
- Edge cases across data, timing, state, environment, localisation and accessibility
- Concrete test data for each case (Unicode, boundary dates, empty states, huge inputs)
- Priority and expected behaviour per case
- Markdown, CSV and JSON export
AI Edge Case Generator example
Form → edge cases
Input:
Profile form: names 1–60 chars any script, DOB 18+, optional E.164 phoneOutput:
EC-01 Name of exactly 60 Arabic characters with diacritics
EC-02 Date of birth exactly 18 years ago today
EC-03 Phone with leading + but spaces
…Frequently asked questions about AI Edge Case Generator
Which categories of edge cases are covered?
Ten: data (Unicode, emoji, right-to-left text, lengths, numeric extremes), timing (double submits, expiry during use, leap days, time zones), state (interrupted flows, stale data), environment (offline, slow network, old browsers, small screens), localisation, accessibility, scale, security, network and permissions.
How is an edge case different from a negative scenario?
An edge case is a valid but unusual condition — a name of 60 Arabic characters, a date of birth exactly 18 years ago, a session that expires mid-form. A negative scenario is misuse or failure, such as bypassing validation or two conflicting updates; the AI Negative Scenario Generator covers those.
What test data does each case come with?
The exact value or setup that reproduces it — such as a name at the maximum length, text with emoji or right-to-left characters, or a date on 29 February — so the case can be run as written.
Technical notes
Each edge case has an ID (EC-01, EC-02 …), a category (data, timing, state, environment, localisation, accessibility, scale, security, network or permissions), a priority, a description of the unusual condition, the exact test data or setup to reproduce it, and the expected behaviour. Cases are spread across the categories that apply rather than padded with near-duplicates.
References
- ISTQB Certified Tester Foundation Level (CTFL) v4.0The foundation syllabus of software testing: test levels and types, test design techniques, test management and tools.
- ISTQB GlossaryThe standard definitions of testing terms — test case, regression testing, severity, priority, boundary value analysis and the rest.
- OWASP Cheat Sheet Series: Input ValidationAllow-list validation, syntactic vs. semantic checks, and why client-side validation is never a security control.