package com.example;

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class MainTest {
    @Test
    @DisplayName("manipulateArray multiplies and adds correctly for positive numbers")
    void testManipulateArrayPositive() {
        int[] input = {1, 2, 3};
        int[] expected = {3, 5, 7}; // (1*2+1, 2*2+1, 3*2+1)
        int[] result = com.example.Main.manipulateArray(input, 2, 1);
        assertArrayEquals(expected, result, "Should correctly multiply and add each element");
    }

    @Test
    @DisplayName("manipulateArray does not modify original array")
    void testOriginalArrayNotModified() {
        int[] input = {4, 5, 6};
        int[] copy = input.clone();
        com.example.Main.manipulateArray(input, 3, 2);
        assertArrayEquals(copy, input, "Original array should not be modified");
    }

    @Test
    @DisplayName("manipulateArray handles empty array")
    void testEmptyArray() {
        int[] input = {};
        int[] expected = {};
        int[] result = com.example.Main.manipulateArray(input, 10, 100);
        assertArrayEquals(expected, result, "Empty input should return empty output");
    }

    @Test
    @DisplayName("manipulateArray handles negative numbers and zero")
    void testNegativeAndZero() {
        int[] input = {-1, 0, 2};
        int[] expected = {-4, -2, 2}; // (-1*2+-2, 0*2+-2, 2*2+-2)
        int[] result = com.example.Main.manipulateArray(input, 2, -2);
        assertArrayEquals(expected, result, "Should handle negative numbers and zero");
    }

    @Test
    @DisplayName("manipulateArray returns a new array instance")
    void testReturnsNewArray() {
        int[] input = {1, 2, 3};
        int[] result = com.example.Main.manipulateArray(input, 1, 1);
        assertNotSame(input, result, "Returned array should be a new instance");
    }
}

MainTest.java

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Challenge: Parameter Manipulation

Solution