test.js

process.env.NODE_ENV = 'test';

const { EventEmitter } = require('events');
const { expect } = require('chai');
const sinon = require('sinon');

const promCollector = require('rewire')('./');

describe('socket.io metrics: internal functions', () => {
  // retrieve unexported functions
  const byteLen = promCollector.__get__('byteLen');
  const beforeHook = promCollector.__get__('beforeHook');

  it('byteLen works with UTF8 string', () => {
    expect(byteLen('Шамиль')).to.eq(12);
  });

  it('byteLen works with non-UTF8 string', () => {
    expect(byteLen('Shamil')).to.eq(6);
  });

  it('byteLen works with object', () => {
    expect(byteLen({ message: 'Hello World!' })).to.eq(26);
  });

  it('byteLen works with Buffer', () => {
    expect(byteLen(Buffer.from('hello world'))).to.eq(11);
  });

  it('byteLen returns 0 on exception or undefined', () => {
    const obj = {};
    obj.a = { b: obj };

    expect(byteLen(obj)).to.eq(0);
    expect(byteLen(undefined)).to.eq(0);
  });

  it('beforeHook returns false if first arg is undefined', () => {
    expect(beforeHook()).to.eq(false);
  });

  it('beforeHook must not change returned value', () => {
    const obj = { func: (a) => a };

    beforeHook(obj, 'func', () => {
      // Hook that doesn't use the parameter
    });
    expect(obj.func(10)).to.not.eq(0);
  });

  it('beforeHook must catch hook exceptions', () => {
    const obj = { func: (a) => a };

    beforeHook(obj, 'func', () => {
      throw new Error('something went wrong');
    });
    expect(obj.func(10)).to.eq(10);
  });
});

describe('socket.io metrics: collector', () => {
  const socket = new EventEmitter();
  const io = new EventEmitter();

  promCollector(io);

  // retrieve unexported metrix variable
  const metrics = promCollector.__get__('metrics');

  const { connectedSockets } = metrics;
  const { connectTotal } = metrics;
  const { disconnectTotal } = metrics;
  const { eventsReceivedTotal } = metrics;
  const { eventsSentTotal } = metrics;
  const { bytesReceived } = metrics;
  const { bytesTransmitted } = metrics;

  const sandbox = sinon.createSandbox();

  afterEach(() => {
    sandbox.restore();
  });

  it('on connect - connectTotal and connectedSockets should increment', () => {
    sandbox.spy(connectTotal, 'inc');
    sandbox.spy(connectedSockets, 'inc');

    io.emit('connect', socket);
    expect(connectTotal.inc.callCount).to.eq(1);
    expect(connectedSockets.inc.callCount).to.eq(1);
  });

  it('on socket disconnect - disconnectTotal should increment and connectedSockets should decrement', () => {
    sandbox.spy(connectedSockets, 'dec');
    sandbox.spy(disconnectTotal, 'inc');

    socket.emit('disconnect');
    expect(connectedSockets.dec.callCount).to.eq(1);
    expect(disconnectTotal.inc.callCount).to.eq(1);
  });

  it('on socket emit - bytesTransmitted and eventsSentTotal should increment', () => {
    const bytesTransmittedInc = sandbox.spy();
    const eventsSentTotalInc = sandbox.spy();

    sandbox.stub(bytesTransmitted, 'labels').returns({ inc: bytesTransmittedInc });
    sandbox.stub(eventsSentTotal, 'labels').returns({ inc: eventsSentTotalInc });

    socket.emit('test event');
    expect(bytesTransmittedInc.callCount).to.eq(1);
    expect(eventsSentTotalInc.callCount).to.eq(1);
  });

  it('on socket emit newListener - bytesTransmitted and eventsSentTotal should not increment', () => {
    const bytesTransmittedInc = sandbox.spy();
    const eventsSentTotalInc = sandbox.spy();

    sandbox.stub(bytesTransmitted, 'labels').returns({ inc: bytesTransmittedInc });
    sandbox.stub(eventsSentTotal, 'labels').returns({ inc: eventsSentTotalInc });

    socket.emit('newListener');
    expect(bytesTransmittedInc.callCount).to.eq(0);
    expect(eventsSentTotalInc.callCount).to.eq(0);
  });

  it('on socket event - bytesReceived and eventsReceivedTotal should increment', (done) => {
    const bytesReceivedInc = sandbox.spy();
    const eventsReceivedTotalInc = sandbox.spy();

    sandbox.stub(bytesReceived, 'labels').returns({ inc: bytesReceivedInc });
    sandbox.stub(eventsReceivedTotal, 'labels').returns({ inc: eventsReceivedTotalInc });

    socket.on('event', () => {
      expect(bytesReceivedInc.callCount).to.eq(1);
      expect(eventsReceivedTotalInc.callCount).to.eq(1);
      done();
    });

    socket.emit('event');
  });

  it('on socket disconnect event - bytesReceived and eventsReceivedTotal should not increment', (done) => {
    const bytesReceivedInc = sandbox.spy();
    const eventsReceivedTotalInc = sandbox.spy();

    sandbox.stub(bytesReceived, 'labels').returns({ inc: bytesReceivedInc });
    sandbox.stub(eventsReceivedTotal, 'labels').returns({ inc: eventsReceivedTotalInc });

    socket.on('disconnect', () => {
      expect(bytesReceivedInc.callCount).to.eq(0);
      expect(eventsReceivedTotalInc.callCount).to.eq(0);
      done();
    });

    socket.emit('disconnect');
  });
});