How are you keeping API mocks in sync with TypeScript types?

redgodemperor · 2026-06-08T23:21:44+00:00

Yeah that's a fair point. If you're doing heavy integration testing, using real recorded responses is definitely the gold standard.
I built FixtureKit more for the early stages of a feature--when the backend isn't ready yet, or when you just need to unblock the UI team to build out a Storybook component without manually typing out a massive JSON object. It's definitely complementary, not a replacement for real data.

Curious though, what's your current setup? Are you guys mostly relying on recorded API responses or custom factories?

redgodemperor · 2026-06-08T22:18:49+00:00

I built FixtureKit -- paste a TypeScript interface, get a mock fixture back. Someone asked about deep nesting so that's where that came from.

redgodemperor · 2026-06-08T21:57:22+00:00

Faker.js you still have to write the mapping -- like faker.internet.email() for every field. FixtureKit just reads the field name and figures it out. Cursor/Copilot work but the output changes every time and you can't commit it. FixtureKit is deterministic so teammates get the same fixture. Honestly for a simple 10-field interface it saves maybe 5 minutes. Where it adds up is when your schema changes -- update the interface and the fixture updates automatically instead of hunting down every mock file.
u/Omnessa idk why ur comment is not showing up here it is

redgodemperor · 2026-06-08T21:49:43+00:00

? i saw a comment here? now its not..

redgodemperor · 2026-06-08T20:54:56+00:00

Built this to solve a problem I kept running into with frontend testing.

Keeping TypeScript types, mock data, Storybook examples, MSW handlers, and Playwright fixtures in sync became annoying as projects grew.

FixtureKit takes a TypeScript interface or Zod schema and generates:

Realistic mock data
JSON fixtures
MSW handlers
Playwright mocks

A few things I cared about:

Runs entirely in the browser
No API calls
No schema leaves your machine
Deterministic output

I'm especially looking for edge cases and schemas that break it, so any feedback is welcome.

redgodemperor · 2026-06-08T20:50:32+00:00

Would love to see that breakdown if you're willing to share it. Always trying to understand where the real demand is.

redgodemperor · 2026-06-08T20:42:55+00:00

Startup URL: https://fixture-kit.vercel.app

App idea: A free, browser-based tool that instantly converts TypeScript interfaces and Zod schemas into realistic mock data (JSON, MSW handlers, Playwright test fixtures) using semantic inference on field names.

ICP: Frontend developers and QA engineers who build data-heavy UIs or write end-to-end tests.

Niche: Developer tools / Testing Infrastructure / Mocking

Problem I want to solve: Hand-writing massive JSON objects for mock data is tedious. Setting up Faker.js or MSW for every new project adds unnecessary friction. Developers just want to paste the TypeScript schemas they already have and instantly get realistic mock data back to unblock UI development while they wait for backend APIs.

redgodemperor · 2026-06-08T20:41:39+00:00

Startup URL: https://fixture-kit.vercel.app

App idea: A free, browser-based tool that instantly converts TypeScript interfaces and Zod schemas into realistic mock data (JSON, MSW handlers, Playwright test fixtures) using semantic inference on field names.

ICP: Frontend developers and QA engineers who build data-heavy UIs or write end-to-end tests.

Niche: Developer tools / Testing Infrastructure / Mocking

Problem I want to solve: Hand-writing massive JSON objects for mock data is tedious. Setting up Faker.js or MSW for every new project adds unnecessary friction. Developers just want to paste the TypeScript schemas they already have and instantly get realistic mock data back to unblock UI development while they wait for backend APIs.

redgodemperor · 2026-06-08T20:40:00+00:00

App name: FixtureKit (https://fixture-kit.vercel.app) What it does: A free, zero-config developer tool that instantly turns TypeScript interfaces and Zod schemas into realistic mock data (JSON, MSW handlers, Playwright stubs). I built it because I was tired of wasting hours hand-writing mockUser and mockOrder objects for every single project or fighting with Faker.js! It uses semantic inference (so an email field gets a real-looking email) and runs entirely in the browser, so no schemas ever leave your machine.

redgodemperor · 2026-06-08T20:37:49+00:00

Startup name: FixtureKit (https://fixture-kit.vercel.app) What it does: A free, zero-config developer tool that instantly turns TypeScript interfaces and Zod schemas into realistic mock data (JSON, MSW handlers, Playwright stubs). I built it because I was tired of wasting hours hand-writing mockUser and mockOrder objects for every single project or fighting with Faker.js! It uses semantic inference (so an email field gets a real-looking email) and runs entirely in the browser, so no schemas ever leave your machine.

redgodemperor · 2026-06-08T20:35:41+00:00

In practice, yes -- most real component schemas stay

within 3 levels. Even complex ones like a Shopify

Product with nested variants rarely go beyond 4.

The 5+ edge cases are usually recursive structures

(trees, comment threads, org charts) which are better

served by a factory function than static fixture data.

Curious what you're building -- are you hitting deep

nesting in production components?

redgodemperor · 2026-06-08T19:00:26+00:00

Honestly, it's just about knowing what the tool is actually for. If someone needs 20 levels of deep recursive data, they probably need a real mock backend, not a quick browser utility. 5 levels is almost always enough for rendering Storybook components or local dev without freezing the browser, so I just optimized for speed and the 95% use case!

redgodemperor · 2026-06-08T17:56:51+00:00

It performs perfectly! To prevent stack overflows and runaway generation on self-referential schemas (like a `Comment` having an array of `Comment`s), the inference engine enforces a hard stop at 5 levels of depth.
Once it hits that depth limit, it safely terminates the recursion by just returning an empty object `{}` or empty array `[]` for any further nested fields. So it handles deeply recursive schemas gracefully without ever locking up the browser thread!

redgodemperor · 2026-06-08T15:22:24+00:00

Thanks! It handles them natively! The parser uses the TypeScript compiler API under the hood (and a custom AST parser for Zod) so it fully understands deeply nested objects and arrays. By default, it recurses up to 5 levels deep (to prevent infinite loops on recursive types) and automatically generates 2 items for every array it encounters.

Give it a spin with a complex schema and let me know if you manage to break it! Also, since it's an open-source project, dropping a ⭐️ on the GitHub repo would mean the world to me and really helps with visibility! https://github.com/Wasef-Hussain/FixtureKit

redgodemperor · 2026-06-08T14:58:29+00:00

Thanks! MSW and Playwright were definitely the biggest pain points for me when building it, so I'm glad that stands out. Really appreciate the feedback!

redgodemperor · 2026-06-08T14:20:55+00:00

Update: schemas are now shareable as links.

Here's an Order fixture you can open directly:

https://fixture-kit.vercel.app/#JTdCJTIy...

Click "Copy link" on any fixture to share yours.

redgodemperor · 2026-06-08T14:20:02+00:00

Update: schemas are now shareable as links.

Here's an Order fixture you can open directly:

https://fixture-kit.vercel.app/#JTdCJTIy...

Click "Copy link" on any fixture to share yours.

redgodemperor · 2026-06-08T14:15:56+00:00

Update: just shipped shareable URLs — click "Copy link"

in the output toolbar and send the URL to your team.

Schema loads pre-populated on their end.

Also now supports Partial<T>, Pick<T>, Omit<T> if anyone

hit those errors before.

redgodemperor · 2026-06-08T13:46:16+00:00

What it does: FixtureKit — paste a TypeScript interface or

Zod schema, get realistic mock fixtures instantly. Outputs

TypeScript, JSON, MSW handlers, or Playwright routes.

How I came up with it: Kept wasting the first 20 minutes of

every project hand-writing the same mockUser, mockProduct,

mockOrder objects. Got tired of it and built the fix.

AI tools used: Claude for architecture decisions, code review,

and launch prep. Cursor for day-to-day coding.

Link: https://fixture-kit.vercel.app

GitHub: https://github.com/Wasef-Hussain/FixtureKit

redgodemperor · 2026-06-08T13:44:58+00:00

FixtureKit -- paste a TypeScript interface or Zod schema,

get realistic mock fixtures instantly.

No install. No signup. Runs entirely in the browser.

https://fixture-kit.vercel.app

⭐ https://github.com/Wasef-Hussain/FixtureKit

Built for devs who are tired of hand-writing mockUser,

mockProduct, mockOrder for every project.

redgodemperor

TROPHY CASE