package.json

{
  "name": "rx-rover",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "babel-node test.js | faucet",
    "test_debug": "babel-node test.js"
  },
  "author": "",
  "license": "ISC",
  "babel": {
    "presets": [
      "es2015"
    ]
  },
  "dependencies": {
    "babel-cli": "^6.4.5",
    "rx": "^4.0.7",
    "tape": "^4.4.0"
  },
  "devDependencies": {
    "babel-preset-es2015": "^6.3.13",
    "faucet": "0.0.1"
  }
}

test.js

import tape from 'tape'
import {Observable} from 'rx'

tape('position initiale', t => {
	var x= 0, y = 0, o = 'N';
	var marsRover = {x, y , o}; 
	const SUT = Observable.of(marsRover)
	SUT
		.tap(valeur => t.deepEqual(valeur, marsRover))
		.subscribe(() => t.end())
})

tape('nouvelle position', t => {
	var marsRover= new MarsRover(0,0,'N');

	const SUT = Observable.of(marsRover)
	const commands = Observable.from(['f'])

	commands
		.map(valeur => {
			marsRover.move(valeur);
			return marsRover;
		})
		.tap( valeur => 
				t.deepEqual(valeur, new MarsRover(0,1,'N'))
			)
		.subscribe(() => t.end())
})

tape('nouvelle position', t => {
	var marsRover= new MarsRover(0,0,'N');

	const SUT = Observable.of(marsRover)
	const commands = Observable.from(['b'])

	commands
		.map(valeur => {
			marsRover.move(valeur);
			return marsRover;
		})
		.tap( valeur => 
				t.deepEqual(valeur, new MarsRover(0,-1,'N'))
			)
		.subscribe(() => t.end())
})

function MarsRover(x,y,o){
	this.x=x;
	this.y=y;
	this.o=o;
}
MarsRover.prototype.move =function(direction){
	var directions = {'N':{x:0,y:1},'S':{x:0,y:-1},'E':{x:1,y:0},'W':{x:-1,y:0}};
		
		if(direction=='f'){
			this.x+=directions[this.o].x;
			this.y+=directions[this.o].y;
		}else{
			this.x-=directions[this.o].x;
			this.y-=directions[this.o].y;
		
		}
	}