API Reliability & Upgrade Toolkit
A practical engineering toolkit for teams that need to upgrade dependencies, validate API contracts, and debug payment integrations without breaking production.
This bundle combines three high-value workflows:
• Turn risky dependency upgrades into ordered, testable patch plans.
• Convert OpenAPI specifications into executable mock servers and contract tests.
• Test Stripe webhook signatures, retries, failures, and idempotency locally.
Built for backend engineers, SaaS developers, API teams, and full-stack teams maintaining production applications.
Instead of debugging migrations and integrations manually, this bundle gives you a repeatable workflow for safer upgrades, API testing, and payment reliability.
Works with every agent that reads SKILL.md — Claude Code, Cursor, Codex CLI, Gemini CLI, GitHub Copilot, Windsurf, OpenClaw, and more.
One payment, lifetime access. 3 skills unlock instantly in your library.
What's included
3 skills
Turn an OpenAPI spec into an executable local mock server, deterministic fixtures, constraint-derived negative tests, and an endpoint coverage report.
Turn risky dependency upgrades into an ordered patch plan that maps affected code, separates mechanical edits from semantic migrations, and validates each step with the repository’s own build and test tooling.
Trigger, sign, replay, and debug Stripe webhook events locally—then verify signature handling, HTTP behavior, and idempotency defenses with a structured test report.
See it in action
OpenAPI-to-Mock Test Harness Builder
Example session with this skill installed
Build a local mock and contract-test harness from:
openapi.yaml
Requirements
- parse the full OpenAPI document;
- inventory every documented operation;
- resolve local $ref references;
- prefer explicit examples already present in the spec;
- generate deterministic valid request and response fixtures when examples are missing;
- generate negative cases from required fields, enums, primitive types, string constraints, numeric bounds, array constraints, and required parameters;
- generate a local mock server for all documented routes;
- include representative documented 4xx/5xx responses when available;
- generate positive contract tests;
- generate concrete negative tests where the schema provides enough information;
- flag unresolved external references instead of inventing schemas;
- do not call production APIs;
- do not embed real credentials;
- generate an endpoint coverage report;
- run validation and tests when the local dependencies are available.
Use the repository's existing API-test/mock stack if one is already configured. Otherwise, generate the default Python/FastAPI/pytest harness.
- Read your context and instructions
- Compiled the openapi-to-mock test harness
OpenAPI mock/test harness complete
OpenAPI version
3.1.0
API
Commerce API
Operations discovered
42
Success fixtures generated
42
Request fixtures generated
27
Documented error fixtures generated
18
Constraint-derived negative cases
96
Mock routes generated
42
Positive contract tests
42
Concrete negative tests
71
Manual-review negative cases
25
Unresolved references
0
Coverage summary
Operations with success fixtures
42 / 42
Operations with positive tests
42 / 42
Operations with at least one negative case:
34 / 42
Operations with documented error fixtures
18 / 42
Operations requiring manual review
5
Harness coverage
100% route generation
81% operations with negative coverage
This is harness coverage, not production code coverage.
Example endpoint
POST /customers
Generated valid request
{
"name": "Example Customer",
"email": "user@example.test",
"plan": "pro"
}
Generated success fixture
{
"id": "00000000-0000-4000-8000-000000000001",
"name": "Example Customer",
"email": "user@example.test",
"plan": "pro"
}
Constraint-derived tests
email:
- required field missing
- wrong primitive type
- invalid email format
plan:
- enum violation
name:
- below minLength
- above maxLength
Generated local server
Run
python -m pip install -r requirements.generated.txt
uvicorn mock_server.app:app --reload --port 4010
Mock URL
Example generated test
def test_create_customer_happy_path():
response = client.post(
"/customers",
json={
"name": "Example Customer",
"email": "user@example.test",
"plan": "pro"
},
)
assert response.status_code == 201
Example negative test
def test_create_customer_missing_email():
payload = {
"name": "Example Customer",
"plan": "pro"
}
response = client.post("/customers", json=payload)
assert response.status_code in {400, 422}
Files generated
- api_inventory.json
- fixtures/
- negative_cases.json
- mock_server/app.py
- tests/test_contracts.py
- requirements.generated.txt
- coverage_report.json
- validation_report.md
- README.generated.md
Validation
Fixture JSON parsing: PASS
Local reference resolution: PASS
Mock server import: PASS
Contract tests: PASS
This harness validates the generated mock contract against the OpenAPI document. It does not prove that the production backend implements the same behavior unless the same contract tests are also run against that backend.
How to use
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