Unit Test Generator
The Unit Test Generator produces a complete test suite for any function, method, or class you provide. It goes beyond the "happy path" to include edge cases, boundary conditions, error scenarios, and null/empty input handling that developers commonly overlook.
Developers at any level use this template to bootstrap test suites for existing code (especially legacy code with no tests), to verify their own test coverage is thorough, or to learn testing patterns for unfamiliar frameworks. It works with any language and testing framework.
The prompt is effective because it uses a systematic categorization of test types (happy path, edge cases, error handling, boundary values) rather than generating random test cases. This ensures comprehensive coverage and teaches the developer to think about testing categories they may have missed.
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The Prompt
Generate a complete unit test suite for the following code: **Programming Language**: [LANGUAGE, e.g., TypeScript, Python, Java] **Testing Framework**: [FRAMEWORK, e.g., Jest, pytest, JUnit] **Code to Test**: ``` [PASTE YOUR FUNCTION, METHOD, OR CLASS HERE] ``` Generate tests organized into these categories: 1. **Happy Path Tests**: Test the normal, expected behavior with typical inputs. Cover the main use cases the function was designed for. 2. **Edge Case Tests**: Test boundary conditions including: - Empty inputs (empty strings, empty arrays, zero values) - Single-element inputs - Maximum/minimum values - Null or undefined inputs (if the language allows) 3. **Error Handling Tests**: Test that errors are thrown or handled correctly for: - Invalid input types - Out-of-range values - Missing required parameters - Malformed data 4. **Boundary Value Tests**: Test values at the exact boundaries of conditions (e.g., if a function checks `x > 10`, test with 9, 10, and 11). For each test: - Use descriptive test names that explain the scenario: `should return empty array when input array is empty` - Include Arrange/Act/Assert sections (or Given/When/Then) - Add a brief comment explaining WHY this test case matters - Use realistic test data, not placeholder values like "test" or "foo" After the test suite, list any additional test scenarios that would require mocking external dependencies, and explain what to mock and why.
Usage Tips
- Include the full function signature and types: The more context you provide (parameter types, return type, docstring), the more targeted the tests will be.
- Specify your testing framework: Jest, pytest, JUnit, and Go's testing package all have different conventions. Specifying yours ensures the output is copy-paste ready.
- Review and prune: The generator intentionally over-produces tests. Remove any that test implementation details rather than behavior, as those create brittle tests.
- Use as a coverage checklist: Even if you prefer writing tests by hand, run this prompt first and compare against your own tests to catch gaps.
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