Engineering

Test Case Generator

Generate edge-case-focused test scenarios for any function, feature, or API endpoint — covering boundary values, failure modes, and regression risks.

Overview

Writing complete tests requires thinking beyond the happy path: boundary values, empty inputs, concurrency issues, permission edge cases. Set this up once and use it to systematically enumerate test scenarios for any function or feature — producing structured test ideas your team can implement in their preferred testing framework.

Workflow

Describe the target
Paste the function signature, feature spec, or API endpoint description.
Specify the framework
Optionally mention your testing framework (xUnit, Jest, pytest) so scenario names match conventions.
Run through the assistant
Send the description with this system prompt to your AI model.
Prioritize and implement
Review the generated scenarios, prioritize by risk, and implement the most critical ones first.

Why This Workflow Works

Categorizing test cases by type (boundary, permission, concurrency) ensures systematic coverage rather than ad-hoc enumeration
Requesting scenarios not code keeps the output implementation-agnostic — works for any framework or language
Regression risk section forces the AI to reason about future failure modes, not just current behavior
Flagging cases that require mocking surfaces test infrastructure decisions before implementation begins

Best for

Functions with non-trivial input validation logic
Public API endpoints with permission requirements
Modules at risk of regression after a major refactor
Features where edge-case failures have high user impact

Not for

Generating runnable test code — this produces scenarios, not implementations
Performance or load testing — use a dedicated benchmarking tool instead
UI pixel-perfect or visual regression testing

Use cases

Generating test plans for a new API endpoint before implementation
Expanding unit test coverage for an undertested module
Creating Playwright or Selenium scenario ideas for E2E test suites
Reviewing a feature spec for testability before writing a single line of code

Customize This Workflow

Pre-fills the System Prompt Generator with this workflow. Customize role, tone, and behavior rules — then generate your prompt.

Open in System Prompt Generator

Prompt Template

You are a senior QA engineer and test architect.

When given a function signature, feature description, or API endpoint, generate a comprehensive set of test cases. Organize them under the following categories:

## Happy Path
The standard, expected behavior under normal conditions.

## Boundary Values
Minimum, maximum, and just-outside-range inputs. Include empty strings, zero values, and null where applicable.

## Error & Failure Cases
Invalid inputs, missing required fields, malformed data, and expected exceptions.

## Permission & Authorization
Access by unauthorized users, expired tokens, and insufficient permissions.

## Concurrency & State
Race conditions, double-submissions, partial state, and concurrent modifications where relevant.

## Regression Risks
Edge cases that are likely to break in future refactors based on the current implementation.

For each test case provide:
- A descriptive test name
- Input / preconditions
- Expected outcome

Do not write the test code — produce test scenarios that the engineer will implement. Flag any cases that require mocking or test doubles.

Related Tools

System Prompt Generator