Not matching public properties?

[eschwartz]

I'm attempting to create a mock for AWS.S3, but I'm getting a error:

error TS2322: Type 'Mock<S3>' is not assignable to type 'S3'.
  Property 'endpoint' is missing in type 'Mock<S3>'.

My code looks like:

import {S3} from "aws-sdk";
import * as TypeMoq from 'typemoq';

function createS3ClientMock():S3 {
  const mock:TypeMoq.Mock<S3> = TypeMoq.Mock.ofType(S3);

  return mock;
}

The definition for S3 looks like:

export declare class S3 {
    constructor(options?: any);
    endpoint: Endpoint;

    getObject(params: s3.GetObjectRequest, callback?: (err: Error, data: any) => void): any;
    putObject(params: s3.PutObjectRequest, callback: (err: Error, data: any) => void): void;
    deleteObject(params: s3.DeleteObjectRequest, callback: (err: Error, data: any) => void): void;
    headObject(params: s3.HeadObjectRequest, callback: (err: Error, data: any) => void): void;
    getSignedUrl(operation: string, params: any): string;
    getSignedUrl(operation: string, params: any, callback: (err: Error, url: string) => void): void;
    upload(params?: s3.PutObjectRequest, options?: s3.UploadOptions, callback?: (err: Error, data: any) => void): void;
    listObjects(params: s3.ListObjectRequest, callback: (err: Error, data: s3.ListObjectResponse) => void): void;
    listObjectsV2(params: s3.ListObjectV2Request, callback: (err: Error, data: s3.ListObjectV2Response) => void): void;
    waitFor(state: string, params: s3.HeadObjectRequest, callback: (err: Error, data: any) => void): void;

    createMultipartUpload(params: any, callback: (err: Error, data: any) => void): void;
    uploadPart(params: any, callback: (err: Error, data: any) => void): void;
    listParts(params: any, callback: (err: Error, data: any) => void): void;
    completeMultipartUpload(params: any, callback: (err: Error, data: any) => void): void;
  }

I'm able to hack my way around this, by doing something like:

function createS3ClientMock():S3 {
  const mock: any = TypeMoq.Mock.ofType(S3);
  mock.endpoint = 'STUBBED_ENDPOINT';
  return <S3> mock;
}

[dizel3d]

function createS3ClientMock():S3 {
  const mock: any = TypeMoq.Mock.ofType(S3);

  // it's wrong way to stub. you should use mock.setup(...)
  mock.endpoint = 'STUBBED_ENDPOINT';

  // you should not cast mock to S3, you should return mock.object
  return <S3> mock;
}

Read README, it's clear enough.

[florinn]

@eschwartz Here is your example modified as suggested by @dizel3d

import { S3, Endpoint } from "aws-sdk";
import * as TypeMoq from "typemoq";

function createS3ClientMock(): S3 {
    const mock = TypeMoq.Mock.ofType(S3);

    // it's wrong way to stub. you should use mock.setup(...)
    mock.setup(x => x.endpoint).returns(() => new Endpoint("STUBBED_ENDPOINT"));

    // you should not cast mock to S3, you should return mock.object
    return mock.object;
}

console.log(createS3ClientMock().endpoint);
//Endpoint {
//  protocol: 'https:',
//  host: 'stubbed_endpoint',
//  port: 443,
//  hostname: 'stubbed_endpoint',
//  pathname: '/',
//  path: '/',
//  href: 'https://stubbed_endpoint/' }

[eschwartz]

Thanks, @florinn for the example.

I kind of the gave up on this, because the documentation on setup is confusing to me. What is the signature of setup? In your example, what is x and why does the function passed to mock.setup return x.endpoint? What does that do?

[florinn]

setup accepts a function (also referred to as 'matcher') taking as input argument the type being mocked (here x having type S3) and as body the value/property/method (with arguments if that's the case) to match (here the getter x.endpoint).