@loopback/testlab/src/sinon.ts

A collection of test utilities we use to write LoopBack tests.

// Copyright IBM Corp. and LoopBack contributors 2018,2020. All Rights Reserved.
// Node module: @loopback/testlab
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

import sinon, {SinonSpy} from 'sinon';

export {sinon, SinonSpy};

export type StubbedInstanceWithSinonAccessor<T> = T & {
  stubs: sinon.SinonStubbedInstance<T>;
};

/**
 * Creates a new object with the given functions as the prototype and stubs all
 * implemented functions.
 *
 * Note: The given constructor function is not invoked. See also the stub API.
 *
 * This is a helper method replacing `sinon.createStubInstance` and working
 * around the limitations of TypeScript and Sinon, where Sinon is not able to
 * list private/protected members in the type definition of the stub instance
 * and therefore the stub instance cannot be assigned to places expecting TType.
 * See also
 *  - https://github.com/Microsoft/TypeScript/issues/13543
 *  - https://github.com/DefinitelyTyped/DefinitelyTyped/issues/14811
 *
 * @typeParam TType - Type being stubbed.
 * @param constructor - Object or class to stub.
 * @returns A stubbed version of the constructor, with an extra property `stubs`
 * providing access to stub API for individual methods.
 */
export function createStubInstance<TType extends object>(
  constructor: sinon.StubbableType<TType>,
): StubbedInstanceWithSinonAccessor<TType> {
  const stub = sinon.createStubInstance(constructor);
  return Object.assign(stub as TType, {stubs: stub});
}