[GEMINI] Add test case for check_for_flag function

tests/test_decoding.py

@@ -133,3 +133,20 @@ def test_try_decode_metadata_rot13_unique_only():
     assert "rot13" not in res_duplicate
 # }}}
 
+# {{{ test_check_for_flag
+def test_check_for_flag():
+    """
+    Verifies that check_for_flag extracts multiple matching flags or returns empty list.
+    """
+    from ctf.decoding import check_for_flag
+    # Default fallback - matches multiple
+    res = check_for_flag("flag{one} and flag{two}")
+    assert set(res) == {"flag{one}", "flag{two}"}
+    # Custom format
+    res_custom = check_for_flag("custom{first} custom{second}", r"custom\{[a-z]+\}")
+    assert set(res_custom) == {"custom{first}", "custom{second}"}
+    # No matches
+    assert check_for_flag("no flag matches here") == []
+# }}}
+
+