diff --git a/test/test_compound_identifier.py b/test/test_compound_identifier.py
index fd588890f..1ea5a4744 100644
--- a/test/test_compound_identifier.py
+++ b/test/test_compound_identifier.py
@@ -27,11 +27,6 @@ def test_is_key_header_positive(compound_identifier, header):
 @pytest.mark.parametrize("header", ["id","smiles","inchi","input", "some_header", "random", "header", ""])
 def test_is_key_header_negative(compound_identifier, header):
     assert not compound_identifier.is_key_header(header)
-
-def test_guess_type_with_inchikey(compound_identifier):
-    inchikey = "LFQSCWFLJHTTHZ-UHFFFAOYSA-N"
-    result = compound_identifier.guess_type(inchikey)
-    assert result == "inchikey"
     
     
 @pytest.mark.parametrize("inchikey", [
@@ -43,6 +38,24 @@ def test_is_inchikey_positive(compound_identifier, inchikey):
     """Test that valid InChIKeys return True."""
     assert compound_identifier._is_inchikey(inchikey) is True
 
+
+@pytest.mark.parametrize("inchikey", [
+    "BSYNRYMUTXBXSQUHFFFAOYSA",        
+    "BSYNRYMUTXBXSQ-UHFFFAOYSA-XY", 
+    "12345678901234-1234567890-X",
+    "BSYNRYMUTXBXSQ_UHFFFAOYSA-N",
+    "BSYNRYMUTXBXSQ-UHFFFAOYSA"
+])
+def test_is_inchikey_negative(compound_identifier, inchikey):
+    """Test that invalid InChIKeys return False."""
+    assert not compound_identifier._is_inchikey(inchikey)
+
+    
+def test_guess_type_with_inchikey(compound_identifier):
+    inchikey = "LFQSCWFLJHTTHZ-UHFFFAOYSA-N"
+    result = compound_identifier.guess_type(inchikey)
+    assert result == "inchikey"
+    
     
 @patch('ersilia.utils.identifiers.compound.CompoundIdentifier._pubchem_smiles_to_inchikey')
 def test_is_smiles_positive_chem_none(mock_pubchem, compound_identifier):