Mars Rover Kata

Source

Your Task

You're part of the team that explores Mars by sending remotely controlled vehicles to the surface of the planet.

Develop an API that translates the commands sent from earth to instructions that are understood by the rover.

Requirements

• You are given the initial starting position (x,y) of a rover and the direction (N,S,E,W) it is facing.

• The rover receives a character array of commands.

• Implement commands that move the rover forward/backward (f,b).

• Implement commands that turn the rover left/right (l,r).

• Implement wrapping at edges. But be careful, planets are spheres:

  • Connect the x edge to the other x edge, so (1,1) for x-1 to (5,1)
  • Connect vertical edges towards themselves in inverted coordinates, so (1,1) for y-1 connects to (5,1).

• Implement obstacle detection before each move to a new square. If a given sequence of commands encounters an obstacle, the rover moves up to the last possible position, aborts the sequence and reports the obstacle.

TODO

• [F] Implement wrapping at edges: Connect the x edge to the other x edge, so (1,1) for x-1 to (5,1)

• [F] Implement wrapping at edges: Connect vertical edges towards themselves in inverted coordinates, so (1,1) for y-1 connects to (5,1).

• [R] Are Rover#rotateLeft and Rover#rotateRight a symptom of the Message Obsession code smell? Is there a way to express the rotation as Rover#rotate(Right|Left)?

• [R] Rover#move receives a Position that might cause the rover to move by more than one step at time. For example: from position (0,0) to (3,5) if we do currentPosition.add(3,5). Is that something we can live with, or we might find a way to limit the position to move at most by 1 unit at a time?

• [R] Is there a better way to express assertEquals(new Rover(new Position(-1, 0), WEST), rover); in the test?

  • Is there a chance to extract a DSL to assert that the rover just moved along a direction?
  • Try to use AssertThat with custom matchers
  • Try to use AssertJ

• [R] Do we still need a class for Commands or we can inline that class as a detail of the Rover? So that we can build the Rover with a list of commands.

• [E] What happens when we supply a not recognized command? Something different than f, b, l, or r.

Questions

• If we had to re-think at the tests of the Rover class, how we might have to rewrite them? What does the Rover class is really doing? Collaborating with the Commands?