diff --git a/tests/test_helpers.py b/tests/test_helpers.py
index 961227b..56f0aa0 100644
--- a/tests/test_helpers.py
+++ b/tests/test_helpers.py
@@ -12,3 +12,20 @@ def test_check_for_flag():
     assert set(res_custom) == {"custom{first}", "custom{second}"}
     assert check_for_flag("no flag matches here") == []
 # }}}
+
+# {{{ test_is_valid_flag
+def test_is_valid_flag():
+    """
+    Verifies that is_valid_flag validates flags and supports uniqueness checks.
+    """
+    from ctf.helpers import is_valid_flag
+    # Valid flag
+    assert is_valid_flag("flag{test}")
+    # Invalid flag
+    assert not is_valid_flag("no flag here")
+    # Uniqueness check (success)
+    assert is_valid_flag("flag{new}", original="flag{old}")
+    # Uniqueness check (failure)
+    assert not is_valid_flag("flag{same}", original="flag{same}")
+# }}}
+