DefaultAttributeMapTest - Refactored

@Test
void testGetSetInt() {
    final DefaultAttributeMap map = new DefaultAttributeMap(null);
    final AttributeKey<Integer> key = AttributeKey.valueOf("int");

    assertThat(map.attr(key)).isNull();

    // Assigning random value to key
    map.setAttr(key, 3653);
    assertThat(map.attr(key)).isEqualTo(3653);

    // Replacing key value with a new random one
    map.setAttr(key, 1);
    assertThat(map.attr(key)).isEqualTo(1);
}