diff --git a/json2xml/dicttoxml.py b/json2xml/dicttoxml.py
index d81115ca..31e21ffe 100755
--- a/json2xml/dicttoxml.py
+++ b/json2xml/dicttoxml.py
@@ -25,9 +25,6 @@
 LOG = logging.getLogger("dicttoxml")  # pragma: no cover
 
 
-ids: list[str] = []  # initialize list of unique ids
-
-
 def make_id(element: str, start: int = 100000, end: int = 999999) -> str:
     """Returns a random integer"""
     return f"{element}_{randint(start, end)}"
@@ -35,6 +32,7 @@ def make_id(element: str, start: int = 100000, end: int = 999999) -> str:
 
 def get_unique_id(element: str) -> str:
     """Returns a unique id for a given element"""
+    ids: list[str] = []  # initialize list of unique ids
     this_id = make_id(element)
     dup = True
     while dup:
@@ -233,6 +231,7 @@ def dict2xml_str(
     """
     parse dict2xml
     """
+    ids: list[str] = []  # initialize list of unique ids
     keys_str = ", ".join(str(key) for key in item)
     if DEBUGMODE:  # pragma: no cover
         LOG.info(
@@ -276,6 +275,7 @@ def list2xml_str(
     item_wrap: bool,
     list_headers: bool = False,
 ) -> str:
+    ids: list[str] = []  # initialize list of unique ids
     if attr_type:
         attr["type"] = get_xml_type(item)
     flat = False
diff --git a/pytest.ini b/pytest.ini
index 1fd9f400..48a7edab 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -1,4 +1,4 @@
 [pytest]
-log_cli = True
-log_cli_level = INFO
+log_cli=True
+log_cli_level=INFO
 
diff --git a/tests/test_dict2xml.py b/tests/test_dict2xml.py
index c3b4fed3..dbb2e752 100644
--- a/tests/test_dict2xml.py
+++ b/tests/test_dict2xml.py
@@ -1,10 +1,7 @@
-import unittest
-
 from json2xml import dicttoxml
 
 
-class TestDict2xml(unittest.TestCase):
-
+class TestDict2xml:
     def test_dict2xml_with_namespaces(self):
         data = {'ns1:node1': 'data in namespace 1', 'ns2:node2': 'data in namespace 2'}
         namespaces = {'ns1': 'http://www.google.de/ns1', 'ns2': 'http://www.google.de/ns2'}
@@ -113,12 +110,33 @@ def test_get_unique_id(self):
         unique_id_elem_4 = dicttoxml.get_unique_id("li")
         assert len(list(set({unique_id_elem_1, unique_id_elem_2, unique_id_elem_3, unique_id_elem_4}))) == 4
 
+    def test_key_is_valid_xml(self):
+        valid_key = "li"
+        invalid_key = "/li"
+        assert dicttoxml.key_is_valid_xml(valid_key) is True
+        assert dicttoxml.key_is_valid_xml(invalid_key) is False
+
     def test_get_xml_type(self):
         assert dicttoxml.get_xml_type("abc") == "str"
         assert dicttoxml.get_xml_type(1) == "int"
         assert dicttoxml.get_xml_type(True) == "bool"
         assert dicttoxml.get_xml_type({}) == "dict"
 
+    def test_is_primitive_type(self):
+        assert dicttoxml.is_primitive_type(True) is True
+        assert dicttoxml.is_primitive_type("abc") is True
+        assert dicttoxml.is_primitive_type({}) is False
+
+    def test_escape_xml(self):
+        elem = "&"
+        escaped_string = dicttoxml.escape_xml(elem)
+        assert "&" != escaped_string
+        assert "&" == escaped_string
+
+    def test_wrap_cdata(self):
+        elem = "li"
+        assert "CDATA" in dicttoxml.wrap_cdata(elem)
+
     def test_list_parent_elements(self):
 
         default_item_func = dicttoxml.default_item_func
diff --git a/tests/test_json2xml.py b/tests/test_json2xml.py
index beaab636..0d3f1bb6 100644
--- a/tests/test_json2xml.py
+++ b/tests/test_json2xml.py
@@ -2,12 +2,10 @@
 
 """Tests for `json2xml` package."""
 
-
+import pytest
 import json
-import unittest
 from collections import OrderedDict
 
-import pytest
 import xmltodict
 from pyexpat import ExpatError
 
@@ -17,7 +15,7 @@
                             readfromurl)
 
 
-class TestJson2xml(unittest.TestCase):
+class TestJson2xml:
     """Tests for `json2xml` package."""
 
     def setUp(self):