diff --git a/standardize_test_format/__init__.py b/standardize_test_format/__init__.py
index e1c1175..c7181a4 100644
--- a/standardize_test_format/__init__.py
+++ b/standardize_test_format/__init__.py
@@ -64,7 +64,8 @@ TEST_PATTERN: re.Pattern = re.compile(
     re.IGNORECASE,
 )
 
-END_SYMBOLS = '.?!'
+END_SYMBOLS_SET = ('.','?','!')
+END_SYMBOLS = ''.join(END_SYMBOLS_SET)
 
 IGNORABLE_WORDS_IN_NAME = frozenset(
     {
@@ -97,7 +98,7 @@ def format_test_prefix(
     if with_javadoc:
         str_builder += ['/** ']
         str_builder += [description]
-        if not description.endswith(END_SYMBOLS):
+        if not description.endswith(END_SYMBOLS_SET):
             str_builder += ['.']
         str_builder += [' */', '\n']