Problem when watching files with custom command

Testem in development mode performs unexpected behavior when I use watch_files (runs twice and exists)

testem.json

{
  "watch_files": [
    "./lib/*",
    "./lib/**/*",
    "./tests/*",
    "./tests/**/*"
  ],
  "launchers": {
    "Node1": {
      "command": "mocha -R tap tests/* tests/**/*",
      "protocol": "tap"
    },
    "Node2": {
      "command": "mocha -R tap tests/* tests/**/*",
      "protocol": "tap"
    }
  },
  "launch_in_dev": [ "Node1", "Node2" ],
  "launch_in_ci": [ "Node1", "Node2" ]
}

Folders structure:

lib folder

lib
├── code
│   └── code.js
└── hello.js

tests folder

tests
├── code
│   └── tests.js
└── tests.js

tests.js looks like this:

ar assert = require('assert');
var hello = require('../lib/hello');

describe('hello', function(){
    it('says hello world', function(done){
        assert.equal(hello(), 'hello world');
        setTimeout(done, 400);
    });
    it('says hello to person', function(done){
        assert.equal(hello('Bob'), 'hello Bob');
        setTimeout(done, 400);
    });
});

Here is how it works (process stops automatically, I don’t do anything)

[gavruk]

@johanneswuerbach https://github.com/gavruk/testem_sample

[Vanuan]

It might be worth to fork https://github.com/airportyh/fireworm/