[JUnit] Introduce to Junit and it annotations

Check the get started guid https://junit.org/junit5/docs/current/user-guide/#overview-getting-help

package com.in28minutes;


import org.junit.jupiter.api.*;

import static org.junit.jupiter.api.Assertions.assertEquals;

/**
 * Before All
 * Before
 * Test
 * After each
 * Before
 * Test
 * After each
 * After All
 * Process finished with exit code 0
 * */
public class MyMathTest {

    @BeforeEach
    public void before( ){
        System.out.println("Before");
    }

    @BeforeAll
    public static void beforeAll( ){
        System.out.println("Before All");
    }

    @Test
    public void sum_with3numbers() {
        System.out.println("Test");
        MyMath math = new MyMath();
        assertEquals(6, math.sum(new int[] {1,2,3}));
    }

    @Test
    public void sum_with1numbers() {
        System.out.println("Test");
        MyMath math = new MyMath();
        assertEquals(3, math.sum(new int[] {3}));
    }

    @AfterEach
    public void after() {
        System.out.println("After each");
    }

    @AfterAll
    public static void afterAll() {
        System.out.println("After All");
    }
}