Type-level Tests and Contract Governance

Protect SDKs, shared packages, and generated API clients with compile-time tests and compatibility rules.

46 min

4 sections

type-tests

sdk

contracts

governance

01. Why Type Tests Exist

Section 1 of 4

Unit tests prove runtime behavior. Type tests prove compile-time behavior. If you publish a design system, SDK, API client, or shared domain package, type tests catch accidental breaking changes that normal tests may never exercise.

typescript

export type CreateTicketInput = {
  customerId: string;
  subject: string;
  priority?: "low" | "normal" | "high";
};

export type TicketSummary = {
  id: string;
  status: "new" | "assigned" | "resolved";
};

export declare function createTicket(input: CreateTicketInput): Promise<TicketSummary>;

Migration, Refactoring, and Any Budgets

Enterprise TypeScript Capstone

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