Test Generator
Commercial use OK
380+ models
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Model:
+ GPT-5, Claude, Gemini
Paste code (or upload a file) and get a complete test suite for your framework of choice — pytest, unittest, Jest, Mocha, Vitest, JUnit, Go test, RSpec, PHPUnit, or XCTest. Pick coverage targets (happy path / edge cases / error cases / property-based) to steer priorities. Free under the daily pool — no Diffblue license, no $50/dev fee.
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Generate unit tests and test suites with free AI. Full code coverage automatically.
How to Use Test Generator
1
Enter your input
Type text, upload a file, or describe what you want. No account needed.
2
Click generate
Our AI processes your request in seconds using the best open-source models.
3
Download & share
Download, copy, or share your result. Free for personal and commercial use.
Use this tool via API
Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.
curl -X POST https://api.free.ai/v1/chat/ \
-H "Authorization: Bearer sk-free-..." \
-H "Content-Type: application/json" \
-d '{"model": "qwen-coder", "messages": [{"role": "user", "content": "Write a Python function that reverses a string."}]}'Test Generator — FAQ
Paste a function, class, or whole file and get back a complete test suite — happy-path cases, edge cases, error cases, and (optionally) property-based tests. Pick the test framework explicitly (pytest / unittest / Jest / Mocha / Vitest / JUnit / Go test / RSpec / PHPUnit / XCTest / etc.) so the output matches your project conventions.
Diffblue Cover is Java-only and starts at $50/dev/month after a free tier capped at small projects. Codium AI (now Qodo) is free for individuals but throttles heavy use and the unit-test mode is optimized for IDE-inline patches, not whole-file suites. Tabnine bundles test generation into its $12/mo Pro plan. Free.ai is 100% free under the daily token pool, supports 9 frameworks across all major languages, and lets you pick coverage targets explicitly (happy / edge / errors / property-based).
Python: pytest for new projects (modern, fixtures, parametrize), unittest for stdlib-only constraints. JavaScript: Vitest (fast Vite-native) or Jest (most popular). TypeScript: Vitest or Jest with ts-jest. Java: JUnit 5. Go: built-in testing package. Ruby: RSpec. PHP: PHPUnit. Swift: XCTest. The picker forces the model to use the exact assertion / fixture syntax for the chosen framework.
Instead of asserting on hand-picked inputs, the model writes Hypothesis (Python), fast-check (JS/TS), or junit-quickcheck (Java) tests that generate hundreds of random inputs and verify a property holds for all of them. Catches bugs hand-written tests miss — off-by-one, integer overflow, empty collection edge cases. Use when the function under test has a clear invariant (sorting, parsing roundtrip, etc.).
No — Free.ai generates the test code; you run it locally. Open /coder/ to drop both files into our browser sandbox and execute, or paste into your local repo and run pytest / npm test / go test as usual. The output includes the exact CLI command for the chosen framework.
The model is told to generate at minimum 1 happy-path, 2-3 edge cases, and (if errors are checked) 1-2 error path tests per public function. For mathematically rigorous coverage use a coverage tool (coverage.py, c8, jacoco) after running — Free.ai targets behavioral coverage, not line coverage.
AI-generated tests are a starting point — they cover the obvious cases fast (happy + standard edges) so you can focus on tricky business invariants. Always read each test before committing; the model occasionally asserts on incorrect expected values when the function name is ambiguous. Treat AI tests like a junior dev's first PR — review, fix, merge.
Better practice is to test through the public API. The model leans toward this. If you explicitly need private-method coverage, mention it in the prompt — the model will use the language's mechanism (Python name mangling, JS dynamic access, Java reflection) but will warn you it's a code smell.
Yes — when the source under test imports DB clients, HTTP clients, file I/O, etc. the model uses the framework's mocking primitive (pytest monkeypatch / unittest.mock, Jest jest.mock, Mockito for Java) and provides minimal fakes. For complex mocks (a 10-method DB session) you'll likely simplify by hand after.
Up to 12,000 characters (~180 lines) on the self-hosted path. Premium long-context Claude/GPT handle full-file (200K+ chars) test runs — switch when generating tests for a full module.
Code is sent to the model, processed, and discarded. Self-hosted Qwen 3 Coder runs on Free.ai's own GPUs — your source never leaves our infrastructure. Premium external models (Claude / GPT-5) route through their providers under their data-handling terms.
Yes — POST to /v1/chat/ with the test system prompt (framework + coverage targets) and the source as the user message. Useful for a CI step that auto-generates tests for new files. See /api/ for snippets.
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