@Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("key=");
        stringBuilder.append(this.key);
        stringBuilder.append(", value=");
        stringBuilder.append(this.value);
        return stringBuilder.toString();
    }
@Test
    public void toStringTest() {
        Tag tag = new Tag(KEY, VALUE);
        Assert.assertEquals(TAG_TO_STRING, tag.toString());
    }