public class Calculator {
    public int add(int a, int b) { return a + b; }
    public double divide(int a, int b) {
        if (b == 0) throw new IllegalArgumentException("Cannot divide by zero");
        return (double) a / b;
    }
}

class CalculatorTest {
    private Calculator calculator;

    @BeforeEach
    void init() { calculator = new Calculator(); }

    @Test
    @DisplayName("Test Addition: 5 + 3 = 8")
    void testAddition() {
        assertEquals(8, calculator.add(5, 3), "5 + 3 should equal 8");
    }

    @Test
    void testDivisionByZero() {
        assertThrows(IllegalArgumentException.class,
            () -> calculator.divide(10, 0));
    }
}

assertEquals(10, 5 * 2, "5 * 2 should equal 10");
assertEquals(3.14, 3.141, 0.01);          // مقارنة بهامش (delta)
assertTrue(5 > 3);
assertNull(nullString);
assertArrayEquals(expected, actual);
assertSame(a, c);                          // نفس مرجع الكائن
assertThrows(IllegalArgumentException.class, () -> calculator.divide(10, 0));
assertTimeout(Duration.ofMillis(100), () -> Thread.sleep(50));

assertAll("Calculator Operations",
    () -> assertEquals(8, calculator.add(5, 3)),
    () -> assertEquals(2, calculator.subtract(5, 3))
);

@ParameterizedTest(name = "{0} + {1} = {2}")
@CsvSource({
    "1, 2, 3",
    "5, 7, 12",
    "-5, 5, 0"
})
void testAdditionWithCsvSource(int a, int b, int expected) {
    assertEquals(expected, new Calculator().add(a, b));
}

@ParameterizedTest
@MethodSource("factorialProvider")
void testFactorial(int input, int expected) {
    assertEquals(expected, new Calculator().factorial(input));
}

static Stream<Arguments> factorialProvider() {
    return Stream.of(Arguments.of(0, 1), Arguments.of(5, 120));
}

@RepeatedTest(value = 5, name = "Repetition {currentRepetition} of {totalRepetitions}")
void testAdditionCommutative() {
    int a = random.nextInt(100), b = random.nextInt(100);
    assertEquals(calculator.add(a, b), calculator.add(b, a));
}

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.10.0</version>
    <scope>test</scope>
</dependency>