Question

Please note: I am new to TDD & cucumber, so the answer may be very easy.

I am creating a basic image editor for a test (the image is just a sequence of letters).
I have written a Cucumber story:

Scenario Outline: edit commands
    Given I start the editor
    And a 3 x 3 image is created
    When I type the command <command>
    Then the image should look like <image> 

The step

Scenarios: colour single pixel
    | command   | image     |
    | L 1 2 C   | OOOCOOOOO |

always fails, returning

  expected: "OOOCOOOOO"
       got: " OOOOOOOO" (using ==) (RSpec::Expectations::ExpectationNotMetError)

This is the step code:

When /^I type the command (.*)$/ do |command|
  @editor.exec_cmd(command).should be
end

The function exec_cmd in the program recognizes the command and launches the appropriate action. In this case it will launch the following

def colorize_pixel(x, y, color)
  if !@image.nil?
    x = x.to_i 
    y = y.to_i
    pos = (y - 1) * @image[:columns] + x
    @image[:content].insert(pos, color).slice!(pos - 1)
  else
    @messenger.puts "There's no image. Create one first!"
  end
end

However, this always fails unless I hardcode the values of the two local variables (pos and color) in the function in the program itself.

Why? It doesn’s seem I’m doing anything wrong in the program itself: the function does what it’s supposed to do and those two variables are only useful locally. So I’d think this is a problem with my use of cucumber. How do I properly test this?

—edit—

def exec_cmd(cmd = nil)
  if !cmd.nil? 
    case cmd.split.first
      when "I" then create_image(cmd[1], cmd[2])
      when "S" then show_image
      when "C" then clear_table
      when "L" then colorize_pixel(cmd[1], cmd[2], cmd[3])
    else
      @messenger.puts "Incorrect command. " + "Commands available: I C L V H F S X."
    end
  else 
    @messenger.puts "Please enter a command."
  end
end

Answer 1

It’s not a cucumber issue.

The problem was that, in exec_cmd, split was called only in the “case” clause, not in the “when”s. This meant that, since the command’s format was “a 1 2 b”, cmd[1] in the “when” would call the second character of the string, a space, not the second value of the array, and the other functions would convert that to_i, returning 0.

I changed exec_cmd like this:

def exec_cmd(cmd = nil)
  if !cmd.nil?
    cmd = cmd.split
    case cmd.first
    when "I" then create_image(cmd[1], cmd[2])
    [...]
end

which fixed the issue.