Test Case Generator
Generate unit test templates for Jest, Vitest, or Mocha from a function signature
About this ToolHow it works, benefits & use casesTap to collapse
The Test Case Generator scaffolds a unit-test file from a function you paste in. It parses the function declaration to pull out its name and parameter list, then emits a ready-to-edit suite for Jest, Vitest, or Mocha with Chai — including the correct import line for each framework. The generated describe block always covers three baseline scenarios: a valid-input test, an edge-case test that passes null arguments, and an invalid-input test that asserts the function throws. Toggle "Include setup / teardown" to add beforeEach and afterEach hooks, and toggle "Async tests" to make each case async and switch the throwing assertion to rejects.toThrow with await. Three starter buttons load a simple function, an arrow function, or an async function so you can see the output immediately. The scaffold is a starting point you fill in with real assertions; copy it, download it with a framework-appropriate file name, or share the configuration via URL.
How to Use
- 1Choose your Test framework (Jest, Vitest, or Mocha + Chai) in the Options panel.
- 2Optionally tick "Include setup / teardown" for beforeEach/afterEach hooks and "Async tests" for async/await cases.
- 3Paste the function you want to test into the Function code panel, or load the Simple, Arrow, or Async example.
- 4Click "Generate Test Cases" to produce the describe block with valid-input, edge-case, and error tests.
- 5Copy the result or download it with the suggested file name, then fill in real assertions for your function.
Key Benefits
- Parses the function name and parameters straight from pasted source
- Outputs idiomatic suites for Jest, Vitest, or Mocha + Chai with the right import line
- Always scaffolds three cases: valid input, null edge case, and a throws-on-invalid test
- Optional beforeEach/afterEach hooks via the setup/teardown toggle
- Async mode marks cases async and switches to await ...rejects.toThrow()
- Simple, Arrow, and Async starter examples to try the tool instantly
- Framework-aware download file name and a shareable configuration URL
Common Use Cases
- Bootstrapping a test file for a new utility function so you only fill in assertions
- Switching an existing test skeleton between Jest, Vitest, and Mocha syntax
- Generating an async test scaffold for a function that returns a promise
- Teaching the standard arrange-act-assert structure with a concrete starting point
- Quickly stubbing out the three common test categories before writing real expectations
Options
Paste the function you want to generate tests for
Copy into a test.test.js file
Run to see the generated test scaffold.
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Inside a describe block named after your function, it scaffolds three it() cases: "should handle valid input" (calls the function with placeholder string arguments and expects a defined result), "should handle edge cases" (passes null for each parameter), and "should throw error on invalid input" (passes undefined and asserts the function throws). These are skeletons — you replace the placeholder arguments and assertions with real values.
It runs a regular expression over the pasted code that matches function declarations and const/let/var assignments, including arrow functions, to extract the identifier and the comma-separated parameter list. If it cannot find a match it falls back to a default name of myFunction with a single param1 placeholder, so you may need to rename things for unusual syntax.