Lambda Test Events as Contracts: Schema-Locked Fixtures Across Teams

// events/schemas/order.created.v1.json
{
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "$id": "https://acme.dev/events/order.created.v1.json",
 "title": "order.created",
 "type": "object",
 "required": ["version", "orderId", "tenantId", "totalCents"],
 "properties": {
 "version": { "const": "1" },
 "orderId": { "type": "string", "format": "uuid" },
 "tenantId": { "type": "string", "minLength": 1 },
 "totalCents": { "type": "integer", "minimum": 0 },
 "correlationId": { "type": "string" }
 },
 "additionalProperties": false
}

// scripts/assert-event-fixtures.ts
import Ajv from "ajv";
import addFormats from "ajv-formats";
import { readdirSync, readFileSync } from "node:fs";
import { join } from "node:path";

const ajv = new Ajv({ allErrors: true, strict: true });
addFormats(ajv);

const root = "events";
for (const family of readdirSync(root)) {
 const schema = JSON.parse(readFileSync(join(root, family, "schema.json"), "utf8"));
 const validate = ajv.compile(schema);
 for (const file of readdirSync(join(root, family, "fixtures"))) {
 const doc = JSON.parse(readFileSync(join(root, family, "fixtures", file), "utf8"));
 if (!validate(doc)) {
 throw new Error(`${family}/${file}: ${ajv.errorsText(validate.errors)}`);
 }
 }
}
console.log("all fixtures schema-ok");

# .github/workflows/event-contracts.yml
name: event-contracts
on: [pull_request]
jobs:
 validate:
 runs-on: ubuntu-latest
 steps:
 - uses: actions/checkout@v4
 - run: corepack enable && pnpm i --frozen-lockfile
 - run: pnpm tsx scripts/assert-event-fixtures.ts
 - run: pnpm --filter @acme/events build # emits .d.ts from schema

# ✅ Invoke with repo fixture
aws lambda invoke \
 --function-name orders-handler \
 --payload file://events/order.created/fixtures/happy-path.json \
 /tmp/out.json

# ❌ Hand-edited console event never committed