Ruby 3.0 should be enabled, see this to learn how to do it

Please organize the structure of test fixture as following (although it has been mentioned in the attached link, I'm repeated here again)

describe "<This message should describe the categories of test groups inside this block>" do
  it "<A short message describing this test group>" do
    expect(...).to eq(...) #Assertions
    #Or Test.assert_equals(user_response, reference_response)
  end
end

The "encoded" example is incorrect: "ArNran u rstm5twob e ePb" (24 characters even though it's a 5×5 square).

It should be "ArNran u rstm5twob  e ePb" instead - note the extra space after "wob".

Edit: it looks like the markdown parser is collapsing whitespace even within the code blocks, hence the error. Seems to work when using a non-breaking space character, " ".