Beyond Function Parameters: Using R Options for Dynamic Inputs. Demonstrate the idea behind the post "Using options() to inject a function’s internal variable for reproducible testing" https://brodrigues.co/posts/2025-02-13-testthat.html

R-options.R

calculate_total <- function(items) {
  subtotal <- sum(items)
  tax_rate <- getOption("TAX_RATE", default = 0.1)  # Default 10% tax
  total <- subtotal * (1 + tax_rate)
  return(round(total, 2))
}

# Test the function with default tax rate
cart1 <- c(10, 20, 30)
print(calculate_total(cart1))  # Output: 66.00

# Set a different tax rate for testing
options(TAX_RATE = 0.15)  # Set 15% tax rate
print(calculate_total(cart1))  # Output: 69.00

# Reset the option after testing
options(TAX_RATE = NULL)
print(calculate_total(cart1))  # Output: 66.00 (back to default)