CalculatorSpec.groovy

// CalculatorSpec.groovy
import spock.lang.Specification

class CalculatorSpec extends Specification {

    def "Test calculate method: #a #operation #b = #expectedResult"() {
        given: "A calculator instance"
        def calculator = new Calculator()

        expect: "The calculation should match the expected value"
        calculator.calculate(a, b, operation) == expectedResult

        where: "Define test data"
        a  | b  | operation || expectedResult
        1  | 2  | "+"       || 3
        5  | 3  | "-"       || 2
        4  | 2  | "*"       || 8
        10 | 2  | "/"       || 5
        -1 | 1  | "+"       || 0
        1  | -1 | "-"       || 2
        -2 | -2 | "*"       || 4
        -4 | -2 | "/"       || 2
        1  | 1  | "+"       || 42
    }

    def "Test calculate method with division by zero"() {
        given: "A calculator instance"
        def calculator = new Calculator()

        when: "Perform division by zero"
        calculator.calculate(10, 0, "/")

        then: "An IllegalArgumentException is thrown"
        def exception = thrown(IllegalArgumentException)

        and: "The exception message is correct" 
        exception.message == "Cannot divide by zero"
    }

    def "Test calculate method with invalid operation"() {
        given: "A calculator instance"
        def calculator = new Calculator()

        when: "Perform calculation with invalid operation"
        calculator.calculate(1, 2, "**")

        then: "An IllegalArgumentException is thrown"
        def exception = thrown(IllegalArgumentException)

        and: "The exception message is correct"
        exception.message == "Invalid operation: **"
    }
}

// Calculator.groovy
class Calculator {
    /**
     * Performs arithmetic operations on two integers.
     *
     * @param a         The first integer.
     * @param b         The second integer.
     * @param operation The operation to perform (+, -, *, /).
     * @return The result of the operation.
     * @throws IllegalArgumentException if the operation is invalid or division by zero is attempted.
     */
    int calculate(int a, int b, String operation) {
        switch (operation) {
            case "+": return a + b
            case "-": return a - b
            case "*": return a * b
            case "/":
                if (b == 0) {
                    throw new IllegalArgumentException("Cannot divide by zero")
                }
                return a / b
            default:
                throw new IllegalArgumentException("Invalid operation: " + operation)
        }
    }

    String toString() {
      "Calc"
    }
}