feat: Errors from gax layer

[danieljbruce]

This PR contains tests for ensuring that errors which pass through the gax layer are presented to the user properly using unit tests from a grpc service.

[danieljbruce]

If I add a before hook with the following in it:

checkPort(inputPort, false, done);

the assert.notEqual(err.code, 'EADDRINUSE'); fails, but I am not sure why at this time.

[danieljbruce]

I changed the way this worked entirely to use a third party dev dependency.

[bcoe]

Left a nit, I would always opt for an async/await appraoch, rather than Promise.then these days.

[bcoe]

my advice would be to always use an async/await interface when possible, I think you could replace this with:

await checkPort()

[danieljbruce]

Done

[danieljbruce]

It actually looks like this now:

  async function checkPort(port: string, inUse: boolean, callback: () => void) {
    const isInUse: boolean = await tcpPortUsed.check(
      parseInt(port),
      'localhost'
    );
    assert.strictEqual(isInUse, inUse);
    callback();
  }