MochaJS doesn' seem to work properly

I'm writing tests for my module with MochaJS. You can see current code here. First time it was running correctly and I added more lines (described advanced). For debugging purposes I wrote

bot.use(function(message, next) {
    console.log(message.text);
    console.log(bot);
    next();
});

Of course I was planning to remove it in final version of code... And here strange things start to take place. It calls function it two or even six times.

I removed piece of above-mentioned code, but it still executes it.

I am running mocha with:

node ./node_modules/mocha/bin/_mocha --no-timeouts

What might be the reason of this problem and how to solve it?

via WildeMe