Ruby Rspec Keep getting NoMethodError for Nil class-CodePudding

I'm new to Ruby and am just learning RSpec. I've written a test for a certain method and keep getting the failing test error:

Failure/Error: if @board[5][@move - 1] == EMPTY_CIRCLE

NoMethodError:
  undefined method `-' for nil:NilClass

I know that the code in the Class file does actually work as it should but I just can't seem to get the test to pass.

Here is the Class file code:

class ConnectFour   
    attr_accessor :player_one, :player_two, :move, :current_player, :board

EMPTY_CIRCLE = "\e[37m\u25cb".freeze
YELLOW_CIRCLE = "\u001b[33m\u25cf".freeze
RED_CIRCLE = "\u001b[31m\u25cf".freeze

def initialize
        @board = Array.new(6){Array.new(7,EMPTY_CIRCLE)}
        @player_one = nil  
        @player_two = nil               
end

def play_round
        print_board
        prompt_player
        @move = prompt_move
        place_marker                    
end

def prompt_move
    loop do
      @move = gets.chomp.to_i
      return @move if valid_move?(@move)

      puts "Invalid input. Enter a column number between 1 and 7"           
    end
end

def valid_move?(move)
    @move.is_a?(Integer) && @move.between?(1, 7)
end

    def place_marker
        if @board[5][@move - 1] == EMPTY_CIRCLE
            @board[5][@move - 1] = @current_player.marker
        end
    end
end

And here is the RSpec test code:

describe ConnectFour do
  subject(:game) { described_class.new }
    let(:player){ double(Player) }

describe '#place_marker' do
        context 'when column is empty' do
            before do
                move = 4                
                allow(game).to receive(:move).and_return(4)
            end

            it 'places marker on bottom row' do                         
                game.place_marker
                expect{game.place_marker}.to change{@board[5][3]}   
            end
        end
    end
end

I've tried multiple things but just can't get the test method to recognize the value for @move i'm trying to send it. Any suggestions would be greatly appreciated!.

CodePudding user response：

@move is nil. You're stubbing out a move method (that doesn't seem to exist) to return 4, but this has nothing to do with the @move variable.

Either make sure @move is set, or modify your code so that it actually has a move method and that all direct reads to @move instead use this method, so your stub can work.

CodePudding user response：

Here's how you can stub @move attr_accessor to return a value:

allow(game).to receive(:move=).with(move: 2)