Use an interface on bot to allow mocking and unit testing

[christianrondeau]

TL;DR: I'd like a BotInterface :)

I'm trying out go-slackbot, and as a TDD user, I want to test my handlers. Right now, I have two choices; either I wrap the https://github.com/BeepBoopHQ/go-slackbot/blob/master/bot.go type in my own, or I create a SomethingHandler than then calls a SomethingHandlerImpl, which abstracts away the slackbot.Bot type.

I think a simpler solution would be to reference to an interface instead of a concrete struct type, and add a New overload that receives the bot. Something like:

func New(slackToken string) *BotInterface {
	b := &Bot{Client: slack.New(slackToken)}
	return b
}

interface BotInterface interface {
    // This is what would be passed around
}

type Bot struct {
    // Nothing else changes...
}

I could just make the interface myself, but then I also need to mock MessageHandler (because

go-slackbot/types.go

Line 19 in 58027c0

type MessageHandler func(ctx context.Context, bot *Bot, msg *slack.MessageEvent)

references directly the concrete type), so it becomes complicated :)

The code might not be perfect, but you get the idea. I can then do:

func TestHelloHandler(t *testing.T) {
    ctx := context.TODO()
    bot := MyBotMock{}
    evt := slack.MessageEvent{}

    HelloHandler(ctx, &bot, &evt)

    // Some assertion...
}

What do you think?