Write a robot simulator.

A robot factory's test facility needs a program to verify robot movements.

The robots have three possible movements:

• turn right
• turn left
• advance

Robots are placed on a hypothetical infinite grid, facing a particular direction (north, east, south, or west) at a set of {x,y} coordinates, e.g., {3,8}, with coordinates increasing to the north and east.

The robot then receives a number of instructions, at which point the testing facility verifies the robot's new position, and in which direction it is pointing.

• The letter-string "RAALAL" means:
  • Turn right
  • Advance twice
  • Turn left
  • Advance once
  • Turn left yet again
• Say a robot starts at {7, 3} facing north. Then running this stream of instructions should leave it at {9, 4} facing west.

Execute the tests with:

$ mix test

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant @tag :pending with a # symbol.

For example:

# @tag :pending
test "shouting" do
  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end

Or, you can enable all the tests by commenting out the ExUnit.configure line in the test suite.

# ExUnit.configure exclude: :pending, trace: true

If you're stuck on something, it may help to look at some of the available resources out there where answers might be found.

Inspired by an interview question at a famous company.

It's possible to submit an incomplete solution so you can see how others have completed the exercise.