WIP (NOT DONE): Typescript demo test using dependence injection (DI)

injection_demo.test.ts

// demo class
import Foo, { FunctioDIExample } from './injection_demo';
import * as sinon from 'sinon';

describe('Dependence injection', () => {
  describe('Class', () => {
    let putObject: any;
    let instance: Foo;

    before(() => {
      class FakeS3 {
        putObject() {
          console.log('shouldn\'t show this text');
        }
      }
      const injections = { S3: FakeS3 };

      putObject = sinon.stub(injections.S3.prototype, 'putObject');
      instance = new Foo(injections);
    });

    it('calls dependency method putObject', () => {
      instance.upload();
      sinon.assert.calledOnce(putObject);
    });
  });

  describe('Function', () => {
    let putObject: any;
    let injections: any;
    before(() => {
      class FakeS3 {
        putObject() {
          console.log('shouldn\'t show this text');
        }
      }
      injections = { S3: FakeS3 };
      putObject = sinon.stub(injections.S3.prototype, 'putObject');
    });

    it('calls dependency method putObject', () => {
      FunctioDIExample('arg1', 'arg2', injections);
      sinon.assert.calledOnce(putObject)
    });
  });
});

injection_demo.ts

import * as AWS from 'aws-sdk';

namespace DI {
  export const S3 = AWS.S3;
};

export default class Foo {
  declare s3: AWS.S3;

  constructor(injections: any) {
    const { S3 } = injections;
    this.s3 = new S3({});
  }

  upload() {
    this.s3.putObject();
  }
}

/**
 * Note: Dependency should be the last parameter
 */
export function FunctioDIExample(arg1: string, arg2: string, injections: any) {
  const { S3 } = injections;

  const s3 = new S3({});
  return s3.putObject(arg1, arg2);
}