Introduction to TDD and RSpec

Welcome to your second lesson in this course dedicated to practicing Test Driven Development (TDD) utilizing Ruby and RSpec . In this unit, we will continue adding features to our calculate_discount function. We have five more requirements for you to implement! In this course, the emphasis is placed on hands-on practice, where you'll receive requirements through tests, one at a time. Your objective is to implement code that makes each test pass, simulating a real-world TDD environment. As the course guide, it's akin to being your pair programmer, providing test-driven prompts to hone your skills as you progress.

Understanding the Red-Green-Refactor Cycle

As a reminder, the Red-Green-Refactor cycle is central to TDD, guiding your development process: Red : Start by writing a failing test to define the next step. Green : Implement just enough code to pass the test, focusing on functionality. Refactor : Optimize the code for clarity and efficiency without changing its behavior.

More Requirements for `calculate_discount` Function

In this section, you will enhance the calculate_discount function by implementing five additional requirements: Non-Numeric Price Input Handling : Learn how to validate inputs and handle errors for non-numeric price values. Non-Numeric Discount Input Handling : Understand how to ensure discount inputs are numeric and manage invalid cases effectively. Handling Very Small Prices : Discover techniques to manage very small prices and ensure they adhere to a defined minimum value post-discount. Minimum Discount Percentage Application : Implement logic to apply a minimum discount percentage when provided with a lower percentage. Capping Maximum Discount Amount : Explore methods for capping the discount at a maximum dollar value, ensuring the discount does not exceed this cap. Below is the calculate_discount function that you will enhance by implementing five additional requirements: Ruby def calculate_discount(original_price, discount_percentage) # Placeholder for initial implementation # This version assumes valid numeric inputs and just calculates the discount original_price - (original_price * (discount_percentage / 100.0)) end

7. Non-Numeric Price Input Handling

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Ruby

describe '#calculate_discount' do
  it 'raises an error for non-numeric price inputs' do
    original_price = 'invalid'
    discount_percentage = 10

    expect {
      calculate_discount(original_price, discount_percentage)
    }.to raise_error(TypeError, 'Price must be a valid number')
  end
end

describe '#calculate_discount' do
  it 'raises an error for non-numeric price inputs' do
    original_price = 'invalid'
    discount_percentage = 10

    expect {
      calculate_discount(original_price, discount_percentage)
    }.to raise_error(TypeError, 'Price must be a valid number')
  end
end

Ruby

describe '#calculate_discount' do
  it 'raises an error for non-numeric discount inputs' do
    original_price = 100
    discount_percentage = 'invalid'

    expect {
      calculate_discount(original_price, discount_percentage)
    }.to raise_error(TypeError, 'Discount must be a valid number')
  end
end

describe '#calculate_discount' do
  it 'raises an error for non-numeric discount inputs' do
    original_price = 100
    discount_percentage = 'invalid'

    expect {
      calculate_discount(original_price, discount_percentage)
    }.to raise_error(TypeError, 'Discount must be a valid number')
  end
end

Ruby

describe '#calculate_discount' do
  it 'handles very small prices correctly' do
    original_price = 0.001
    discount_percentage = 1
    expected_discounted_price = 0.01

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

describe '#calculate_discount' do
  it 'handles very small prices correctly' do
    original_price = 0.001
    discount_percentage = 1
    expected_discounted_price = 0.01

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

Ruby

describe '#calculate_discount' do
  it 'applies a minimum 1% discount when lower is provided' do
    original_price = 100
    discount_percentage = 0.1
    expected_discounted_price = 99

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

describe '#calculate_discount' do
  it 'applies a minimum 1% discount when lower is provided' do
    original_price = 100
    discount_percentage = 0.1
    expected_discounted_price = 99

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

Ruby

describe '#calculate_discount' do
  it 'caps the maximum discount amount at $500' do
    original_price = 2500
    discount_percentage = 30
    expected_discounted_price = 2000

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

describe '#calculate_discount' do
  it 'caps the maximum discount amount at $500' do
    original_price = 2500
    discount_percentage = 30
    expected_discounted_price = 2000

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

Ruby

def calculate_discount(original_price, discount_percentage)
  raise TypeError, 'Price must be a valid number' unless original_price.is_a?(Numeric)
  raise TypeError, 'Discount must be a valid number' unless discount_percentage.is_a?(Numeric)

  discount_percentage = [discount_percentage, 1].max
  discount_amount = original_price * (discount_percentage / 100.0)
  discount_amount = [discount_amount, 500].min

  discounted_price = original_price - discount_amount
  [discounted_price, 0.01].max
end

def calculate_discount(original_price, discount_percentage)
  raise TypeError, 'Price must be a valid number' unless original_price.is_a?(Numeric)
  raise TypeError, 'Discount must be a valid number' unless discount_percentage.is_a?(Numeric)

  discount_percentage = [discount_percentage, 1].max
  discount_amount = original_price * (discount_percentage / 100.0)
  discount_amount = [discount_amount, 500].min

  discounted_price = original_price - discount_amount
  [discounted_price, 0.01].max
end

Ruby

describe '#calculate_discount' do
  it 'raises an error for non-numeric price inputs' do
    original_price = 'invalid'
    discount_percentage = 10

    expect {
      calculate_discount(original_price, discount_percentage)
    }.to raise_error(TypeError, 'Price must be a valid number')
  end
end

Ruby

describe '#calculate_discount' do
  it 'raises an error for non-numeric discount inputs' do
    original_price = 100
    discount_percentage = 'invalid'

    expect {
      calculate_discount(original_price, discount_percentage)
    }.to raise_error(TypeError, 'Discount must be a valid number')
  end
end

Ruby

describe '#calculate_discount' do
  it 'handles very small prices correctly' do
    original_price = 0.001
    discount_percentage = 1
    expected_discounted_price = 0.01

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

Ruby

describe '#calculate_discount' do
  it 'applies a minimum 1% discount when lower is provided' do
    original_price = 100
    discount_percentage = 0.1
    expected_discounted_price = 99

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

Ruby

describe '#calculate_discount' do
  it 'caps the maximum discount amount at $500' do
    original_price = 2500
    discount_percentage = 30
    expected_discounted_price = 2000

    result = calculate_discount(original_price, discount_percentage)

    expect(result).to eq(expected_discounted_price)
  end
end

Ruby

def calculate_discount(original_price, discount_percentage)
  raise TypeError, 'Price must be a valid number' unless original_price.is_a?(Numeric)
  raise TypeError, 'Discount must be a valid number' unless discount_percentage.is_a?(Numeric)

  discount_percentage = [discount_percentage, 1].max
  discount_amount = original_price * (discount_percentage / 100.0)
  discount_amount = [discount_amount, 500].min

  discounted_price = original_price - discount_amount
  [discounted_price, 0.01].max
end

Introduction to TDD and RSpec

Understanding the Red-Green-Refactor Cycle

More Requirements for `calculate_discount` Function

7. Non-Numeric Price Input Handling

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8. Non-Numeric Discount Input Handling

9. Handling Very Small Prices

10. Minimum Discount Percentage Application

11. Capping Maximum Discount Amount

Final `calculate_discount` Function

Summary and Preparation for Practice Exercises