Testing Concurrent Requests and Race Conditions
A race that appears once a week is a test waiting to be made deterministic.
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API engineering, from the spec out
Product updates, engineering notes, and guides for designing, debugging, testing, mocking, and serving MCP tools from one OpenAPI spec.
Browse the guidesMocking Region-Specific Latency for Slow-Network Clients
A user in a distant region waits on a different clock than your local machine.
Read articleMocking Multipart Validation Errors for File Upload Forms
A multipart request can fail on one part while the rest are valid.
Read articleMocking Token Expiry Based on Clock Time, Not Request Count
A token expires at a moment in time, so the mock should judge it on the clock.
Read articlePact vs Prism: Which Contract Mocking Tool Fits?
Pact and Prism both touch contracts and mocks, but they start from opposite ends.
Read articleTesting Pagination Boundaries: Catching Off-by-One Errors
The row at the page edge is where one-off errors show up.
Read articleMocking Correlation IDs for Request Tracing
One identifier turns separate service logs into one chain.
Read articleMocking a Race Between Two Clients: A Deterministic Approach
Turn a timing-dependent two-client race into a repeatable set of mock responses.
Read articleMocking GraphQL Partial Data and Errors: A Practical Guide
One GraphQL response can hold both successful fields and failed fields at once.
Read articleWhat Is Contract Drift Between a Mock and an API?
A mock is a frozen snapshot; the real API keeps moving, and the two can quietly diverge.
Read articleMocking API Version Negotiation: Headers, Paths, Fallbacks
Version negotiation decides which contract the server answers with.
Read articleDuplicate HTTP Headers Sent as an Array: How to Debug Them
A header you set once can leave the client as repeated lines and reach the server as an array.
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