How to test a single middeware with tape without a server running - in node or in browser

middlewareTest.js

// This only works if you call - return next - in your middleware. Otherwise the cb (i.e next) won't return anything and the var will be undefined
// And you don't even need node - You can run it in a browser - Totally runtime agnostic
// Reference -> https://github.com/karlpokus/konstapel/blob/master/test/tests.js
var test = require('tape'),
    m = require('module');

test('.usernameIsValid', function(t){
  // mock req, res and next
  var pass = m.usernameIsValid({user: {}}, null, function(){ return true }),
      fail = m.usernameIsValid({}, null, function(err){ return err });
  // test
  t.equal(pass, true, 'calls next if req.user');
  t.equal(fail instanceof Error, true, 'returns error if !req.user');
  // you may even check new props set on req as JS passes objects by reference
  // t.equal(req.user.data, 'much data', 'much data is created');
  t.end();
});

It's actually not necessary to return next to test middleware with tape.

m.usernameIsValid({user: {}}, null, function(){
  t.pass(); // or if error is passed -> t.err()
}),