rover_test.js

    [
        {startsFacing: "N", endsFacing: "E"},
        {startsFacing: "E", endsFacing: "S"},
        {startsFacing: "S", endsFacing: "W"},
        {startsFacing: "W", endsFacing: "N"}
    ].forEach(
        function ({startsFacing, endsFacing}) {
            it(`turns right from ${startsFacing} to ${endsFacing}`, () => {
                let rover = {facing: startsFacing};
                rover = go(rover, "R");
                assert.equal(rover.facing, endsFacing);
            })
        })