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Sharing Data Between Steps

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In Cucumber, sharing data between steps is a crucial aspect of writing efficient and maintainable test scenarios. This section will guide you through the methods and best practices for sharing data between steps in your Cucumber tests.

Key Concepts

  1. State Management: Understanding how to manage and share state between steps is essential for creating coherent and logical test scenarios.
  2. Instance Variables: Using instance variables to store and share data across different steps within the same scenario.
  3. World Object: Leveraging the World object to maintain state and share data across steps.
  4. Hooks for Setup and Teardown: Utilizing hooks to set up and clean up shared data before and after scenarios.

Using Instance Variables

Instance variables are a straightforward way to share data between steps. They are accessible across all steps within the same scenario.

Example

# features/step_definitions/sharing_steps.rb

Given('I have a variable with value {int}') do |value|
  @shared_value = value
end

When('I increment the variable by {int}') do |increment|
  @shared_value += increment
end

Then('the variable should be {int}') do |expected_value|
  expect(@shared_value).to eq(expected_value)
end

Explanation

  • @shared_value: An instance variable that holds the state shared across steps.
  • Given Step: Initializes the variable.
  • When Step: Modifies the variable.
  • Then Step: Asserts the final value of the variable.

Using the World Object

The World object in Cucumber acts as a context for your steps, allowing you to define methods and variables that can be accessed across steps.

Example

# features/support/env.rb

module CustomWorld
  attr_accessor :shared_data
end

World(CustomWorld)

# features/step_definitions/sharing_steps.rb

Given('I set shared data to {string}') do |data|
  self.shared_data = data
end

When('I append {string} to shared data') do |additional_data|
  self.shared_data += additional_data
end

Then('the shared data should be {string}') do |expected_data|
  expect(self.shared_data).to eq(expected_data)
end

Explanation

  • CustomWorld Module: Defines an accessor for shared_data.
  • World(CustomWorld): Extends the World object with the CustomWorld module.
  • Steps: Use self.shared_data to access and modify the shared data.

Practical Exercise

Task

Create a Cucumber scenario that calculates the total price of items in a shopping cart. Use shared data to store the cart's total price and update it as items are added.

Solution

# features/step_definitions/shopping_cart_steps.rb

Given('the cart is empty') do
  @total_price = 0
end

When('I add an item with price {int}') do |price|
  @total_price += price
end

Then('the total price should be {int}') do |expected_total|
  expect(@total_price).to eq(expected_total)
end

Feedback and Tips

  • Common Mistake: Forgetting to initialize shared data can lead to nil errors. Always initialize your shared variables.
  • Tip: Use descriptive variable names to make your steps more readable and maintainable.

Conclusion

Sharing data between steps is a fundamental technique in Cucumber that enhances the reusability and clarity of your test scenarios. By using instance variables and the World object, you can efficiently manage state across steps, leading to more organized and effective BDD tests. In the next section, we will explore advanced Gherkin techniques to further enhance your BDD skills.

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