Please tell me your point of view when writing unit tests on unit.

class HashMapTest{

    private Map<String, String>stringHashMap;

    private Map <String, String > immutableMap;

    @DisplayName ("Initialize per test")
    @BeforeEach
    void init() {
        US>stringHashMap = newHashMap<>();
        US>stringHashMap.put("alice", "hoge";
        US>stringHashMap.put("bob", "fuga");
        immutableMap=Map.of();
    }

    @DisplayName ("Test Value")
    @ Test
    void getTest() {
        assertAll("MapGetTest",
                ( ) - >assertEquals (stringHashMap.get ("alice"), "hoge"),
                ( ) - >assertNotEquals(stringHashMap.get("bob"), "piyo"));

    }

    @DisplayName ("Test Value Settings")
    @ Test
    void putTest() {
        US>stringHashMap.put("carol", "piyo");
        assertAll("MapPutTest",
                ( ) - >assertEquals (stringHashMap.get ("carol"), "piyo"),
                ( ) - >assertNotEquals(stringHashMap.get("dave"), "hoge"));
    }

    @DisplayName ("Exception test for invariant map")
    @ Test
    void immutableTest(){
        assertThrows(UnsupportedOperationException.class,()->impossibleMap.put("key", "value"));
    }
}