Rails rspec error: wrong number of arguments (0 for 1)

Question

I am new to rails and rspec, and currently taking an online a tutorial.

In the tutorial I am running the following code:

def display_board(board)
  puts " #{board[0]} | #{board[1]} | #{board[2]} "
  puts "-----------"
  puts " #{board[3]} | #{board[4]} | #{board[5]} "
  puts "-----------"
  puts " #{board[6]} | #{board[7]} | #{board[8]} "
end

board = [" "," "," "," "," "," "," "," "," "]
display_board(board)

When I run the test I get the following output:

/lib/display_board.rb
  defines a method display_board
  #display_board method
    represents a cell as a string with 3 spaces (FAILED - 1) 

Failures: 

  1) /lib/display_board.rb #display_board method represents a cell as a string with 3 spaces

     Failure/Error:
       def display_board(board)
         puts " #{board[0]} | #{board[1]} | #{board[2]} "
         puts "-----------"
         puts " #{board[3]} | #{board[4]} | #{board[5]} "
         puts "-----------"
         puts " #{board[6]} | #{board[7]} | #{board[8]} "
       end

     ArgumentError:
       wrong number of arguments (0 for 1)
     # ./lib/display_board.rb:2:in `display_board'
     # ./spec/display_board_spec.rb:10:in `block (4 levels) in <top (required)>' 
     # ./spec/spec_helper.rb:5:in `capture_puts'
     # ./spec/display_board_spec.rb:10:in `block (3 levels) in <top (required)>'

Finished in 0.00296 seconds (files took 0.14604 seconds to load)

2 examples, 1 failure

Failed examples:

rspec ./spec/display_board_spec.rb:9 # /lib/display_board.rb #display_board method represents a cell as a string with 3 spaces

The test case is as follows:

it 'represents a cell as a string with 3 spaces' do
  output = capture_puts{ display_board }
  expect(output).to include("   ")
end

Where line 10 is the spec file is "output = capture_puts{ display_board }"

And "capture_puts" is defined in the spec_helpr.rb as follows:

def capture_puts
  begin
    old_stdout = $stdout
    $stdout = StringIO.new('','w')
    yield
    $stdout.string
  ensure
    $stdout = old_stdout
  end
end

I searched for the error "wrong number of arguments (0 for 1)", but I didn't get any useful result. Please advice since I am really a beginner with Ruby and Rails.

Ursus · Accepted Answer · 2016-07-16 11:54:37Z

1

You have to pass the board to display_board

board = [" "," "," "," "," "," "," "," "," "]
output = capture_puts{ display_board(board) }
expect(output).to include("   ")

answered Jul 16, 2016 at 11:54

Ursus

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Comments

nikkypx · Accepted Answer · 2016-07-17 02:36:32Z

0

The error is due to this line

output = capture_puts{ display_board }

display_board requires an argument, so it should look like

output = capture_puts{ display_board(board) }

I also wanted to point out as well that there is an rspec matcher for testing stdout.

https://www.relishapp.com/rspec/rspec-expectations/docs/built-in-matchers/output-matcher

answered Jul 17, 2016 at 2:36

nikkypx

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