Question

So I’m on the first project in “Pragmatic Cucumber” and I’m getting an undefined method error in my step definitions. The error is coming from $?.success?. Needless to say I’m confused. Am I missing a gem or something?

Here’s the Step Definition

Given /^the input "(.*?)"$/ do |input|
  @input = input
end

When /^the calculator is run$/ do
  @output = 'ruby calc.rb #{@input}'
  raise('Command failed!') unless $?.success? #$?.success? is failing. look that up.
end

Then /^the output should be "(.*?)"$/ do |arg1|
  pending # express the regexp above with the code you wish you had
end

Here’s the Error.

Feature: Adding

  Scenario: Add two numbers       # features/adding.feature:3
Given the input "2+2"         # features/step_definitions/calculator_steps.rb:1
When the calculator is run    # features/step_definitions/calculator_steps.rb:5
  undefined method `success?' for nil:NilClass (NoMethodError)
  ./features/step_definitions/calculator_steps.rb:7:in `/^the calculator is run$/'
  features/adding.feature:5:in `When the calculator is run'
Then the output should be "4" # features/step_definitions/calculator_steps.rb:10

Failing Scenarios:
cucumber features/adding.feature:3 # Scenario: Add two numbers

1 scenario (1 failed)
3 steps (1 failed, 1 skipped, 1 passed)
0m0.012s

So, what’s the problem here? I know that .success? is correct, why isn’t $? registering? Thanks!

Answer 1

You need to use backticks instead of quotes to run your command:

@output = 'ruby calc.rb #{@input}'

Should be:

@output = `ruby calc.rb #{@input}`

Edit:

Just tested this – you want to be very careful using this construct. The value of $? won’t be cleared out between Cucumber scenarios, so it would be easy to make an assertion against the result of a command that was run in a previous scenario. You may wish to look into Aruba which is specifically designed for situations where you need Cucumber to execute or assert against command-line programs.