Dev
Unit Test Case Generator
The hardest part of unit testing is often starting — staring at an empty file, trying to remember which cases matter. This generator removes that friction by producing a Jest-compatible describe block with placeholder it cases already labelled for the scenarios that count. Enter the function name and set how many cases you want (1–10). The generator draws labels in order: returns the expected result for typical input, handles edge cases correctly, handles invalid input gracefully, works with boundary values, returns the correct type, handles empty input, handles large input, does not mutate its arguments, is consistent across repeated calls, and matches the documented contract. Labels cycle after ten. Each case has arrange, act, and assert comments with a placeholder assertion. Paste the skeleton into your test directory and fill in real assertions. Works with Jest, Vitest, and Mocha.
How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Enter the name of the function under test.
- Choose how many test cases you want.
- Click Generate to produce the test skeleton.
- Paste it in and replace the placeholders with real assertions.
Use Cases
- •Scaffolding a Jest test file for a new function
- •Ensuring consistent test coverage across a codebase
- •Reminding yourself which cases are worth testing
- •Teaching the arrange-act-assert testing pattern
- •Overcoming the inertia of starting from a blank test file
Tips
- →Always include cases for invalid and empty input, not just the happy path.
- →Rename the it labels to describe the specific behaviour you check.
- →Keep one assertion focus per case for clearer failures.
- →Generate a few extra cases, then delete any that do not apply.
FAQ
which test frameworks does the skeleton work with
The skeleton uses the describe and it structure with expect-style assertions, which is shared by Jest, Vitest, and Mocha. It works with all three without modification.
does it write real assertions
No. Each case contains a placeholder expect(result).toBeDefined() with arrange, act, and assert comments. You replace the placeholder with concrete inputs and the specific outputs you expect — the generator cannot know what your function returns.
what determines the labels on each test case
The generator cycles through a fixed list of ten labels in order: typical input, edge cases, invalid input, boundary values, correct type, empty input, large input, mutation check, consistency, and contract match. Requesting four cases gives you the first four.
how many cases should I generate
Four to six covers the common bases — typical input, edge cases, invalid input, and a boundary check. Generate a few extra and delete the ones that do not apply rather than trying to count exactly upfront.
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