Define behavior before implementation
An endpoint is a promise to its callers. Before choosing a controller or database query, describe the resource, required fields, and valid state transitions. Consider a support ticket: creating it, assigning it, and closing it are different actions with different preconditions. Making those differences explicit keeps clients from guessing what the server will accept.
Treat permissions as part of the contract
Authentication establishes an identity; authorization decides whether that identity can perform an action on a particular resource. For a multi-tenant service, checking a role alone is insufficient. A request must also be scoped to the appropriate tenant and resource. Tests should include a valid user attempting to access another tenant’s record, not just requests without credentials.
Make failures predictable
Clients need a stable way to distinguish invalid input, denied access, missing resources, and temporary service failures. Keep error codes and response shapes consistent, and avoid leaking internal exception details. When a request times out, the caller may not know whether it succeeded. For operations with side effects, define retry behavior and an idempotency strategy before encouraging automatic retries.
Turn the contract into checks
A practical review includes one successful request, boundary values, missing fields, incorrect permissions, and repeated requests. Verify both the response and the stored state. An API can return the expected status while leaving incorrect data behind. Contract tests become most useful when they protect behavior that other services actually depend on.