You might want to enforce the use of regex because some people get around with .slice and equality operators (e.g <, >, <=, >=) to parse the numbers.

No random tests in Coffeescript

• the description isn't giving the info that the output should finish with a new line
• the tests are really bad:
  • my solution passes the tests without that last char
  • but the sample tests are specifically wanting it
  • there are close to no chances that the random tests catch that error
  • no fixed tests
  • the tested coordinates are ranom, but not the inputs
  • (why the hell not testing the full board string!??? xo )

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example test cases would be awesome.

It would be helpful with these test cases, mark that '#' symbols are equal to black cells and ' ' are white cells.