packages/rest/src/__tests__/unit/writer.unit.ts

// Copyright IBM Corp. and LoopBack contributors 2019. All Rights Reserved.
// Node module: @loopback/rest
// This file is licensed under the MIT License.
// License text available at https://opensource.org/licenses/MIT

import {expect, ObservedResponse, stubExpressContext} from '@loopback/testlab';
import {Duplex} from 'stream';
import {Response, writeResultToResponse} from '../..';

describe('writer', () => {
  let response: Response;
  let observedResponse: Promise<ObservedResponse>;

  beforeEach(setupResponseMock);

  it('writes string result to response as text', async () => {
    writeResultToResponse(response, 'Joe');
    const result = await observedResponse;

    // content-type should be 'application/json' since it's set
    // into the response in writer.writeResultToResponse()
    expect(result.headers['content-type']).to.eql('text/plain');
    expect(result.payload).to.equal('Joe');
  });

  it('writes object result to response as JSON', async () => {
    writeResultToResponse(response, {name: 'Joe'});
    const result = await observedResponse;

    expect(result.headers['content-type']).to.eql('application/json');
    expect(result.payload).to.equal('{"name":"Joe"}');
  });

  it('writes boolean result to response as json', async () => {
    writeResultToResponse(response, true);
    const result = await observedResponse;

    expect(result.headers['content-type']).to.eql('application/json');
    expect(result.payload).to.equal('true');
  });

  it('writes number result to response as json', async () => {
    writeResultToResponse(response, 2);
    const result = await observedResponse;

    expect(result.headers['content-type']).to.eql('application/json');
    expect(result.payload).to.equal('2');
  });

  it('writes buffer result to response as binary', async () => {
    const buf = Buffer.from('ABC123');
    writeResultToResponse(response, buf);
    const result = await observedResponse;

    expect(result.headers['content-type']).to.eql('application/octet-stream');
    expect(result.payload).to.equal('ABC123');
  });

  it('writes stream result to response as binary', async () => {
    const buf = Buffer.from('ABC123');
    const stream = new Duplex();
    stream.push(buf);
    stream.push(null);
    writeResultToResponse(response, stream);
    const result = await observedResponse;

    expect(result.headers['content-type']).to.eql('application/octet-stream');
    expect(result.payload).to.equal('ABC123');
  });

  it('writes null object result to response as JSON', async () => {
    writeResultToResponse(response, null);
    const result = await observedResponse;
    expect(result.headers['content-type']).to.eql('application/json');
    expect(result.payload).to.equal('null');
  });

  it('sends 204 No Content when the response is undefined', async () => {
    writeResultToResponse(response, undefined);
    const result = await observedResponse;

    expect(result.statusCode).to.equal(204);
    expect(result.headers).to.not.have.property('content-type');
    expect(result.payload).to.equal('');
  });

  it('skips writing when the return value is the response', async () => {
    response
      .status(200)
      .contentType('text/html; charset=utf-8')
      .send('<html><body>Hi</body></html>');
    writeResultToResponse(response, response);
    const result = await observedResponse;
    expect(result.statusCode).to.equal(200);
    expect(result.headers).to.have.property(
      'content-type',
      'text/html; charset=utf-8',
    );
    expect(result.payload).to.equal('<html><body>Hi</body></html>');
  });

  it('skips writing when the response headers are sent', async () => {
    response
      .status(200)
      .contentType('text/html; charset=utf-8')
      .send('<html><body>Hi</body></html>');
    writeResultToResponse(response, undefined);
    const result = await observedResponse;
    expect(result.statusCode).to.equal(200);
    expect(result.headers).to.have.property(
      'content-type',
      'text/html; charset=utf-8',
    );
    expect(result.payload).to.equal('<html><body>Hi</body></html>');
  });

  function setupResponseMock() {
    const responseMock = stubExpressContext();
    response = responseMock.response;
    observedResponse = responseMock.result;

    // content-type should be undefined since it's not set in the response yet.
    expect(response.getHeader('content-type')).to.eql(undefined);
  }
});