diff --git a/src_v2/parser/parser_internals.nim b/src_v2/parser/parser_internals.nim
index 177c11a..efd91d5 100644
--- a/src_v2/parser/parser_internals.nim
+++ b/src_v2/parser/parser_internals.nim
@@ -239,6 +239,8 @@ when isMainModule:
     # Mismatch
     assert testParser123.flatMap(ch('2')).error().kind == charMismatchErr
     assert testParser123.flatMap(ch(Letters)).error().kind == charMismatchErr
+    assert testParser123.flatMap(str("1234")).error().kind == endOfStringErr
+    assert testParser123.flatMap(str("456")).error().kind == charMismatchErr
 
     # Out of bounds
     # assert initParserResult("").flatMap(ch1).error().kind == endOfStringErr