TestHandlers

TestHandlers<A> = { [K in keyof A]?: A[K] extends (args: infer P) => Promise<infer R> ? (args: […P, ctx: { caller: Principal }]) => R | Promise<R> : never }

Defined in: core/src/testing/test-client.ts:70

The handlers of a mocked canister, typed from the generated Actor of its module: one optional function per method.

A handler takes the method’s arguments as domain values (bigint for a nat, checked principal text for a principal, { tag, value } for a variant) and then a context, { caller }: the principal that sent the call, as checked principal text, after the fake replica verified its signature. It returns what the method returns, or a promise of it. A handler that returns a number for a nat does not compile.

Handlers speak the canister’s shapes, not the client’s. For a method whose one result is an Ok/Err variant a handler returns { tag: "Ok", value } or { tag: "Err", value }, and the client unwraps it: the call resolves with the Ok payload, or rejects canister_err with the Err one. For a method with several results a handler returns the tuple, and for one with none it returns nothing.

Type Parameters

A

A

Example

import { actor, type Actor } from "./canisters/icrc1"

const handlers: TestHandlers<Actor> = {
  icrc1_fee: () => 10_000n,
  icrc1_balance_of: ({ owner }, { caller }) => (owner === caller ? 5n : 0n),
}