diff --git a/swh/model/tests/test_identifiers.py b/swh/model/tests/test_identifiers.py
--- a/swh/model/tests/test_identifiers.py
+++ b/swh/model/tests/test_identifiers.py
@@ -1380,6 +1380,101 @@
         )
 
 
+@pytest.mark.parametrize(
+    "object_type,qualifiers,expected",
+    [
+        # No qualifier:
+        (ObjectType.CONTENT, {}, f"swh:1:cnt:{HASH}"),
+        # origin:
+        (ObjectType.CONTENT, {"origin": None}, f"swh:1:cnt:{HASH}"),
+        (ObjectType.CONTENT, {"origin": 42}, ValueError),
+        # visit:
+        (
+            ObjectType.CONTENT,
+            {"visit": f"swh:1:snp:{HASH}"},
+            f"swh:1:cnt:{HASH};visit=swh:1:snp:{HASH}",
+        ),
+        (
+            ObjectType.CONTENT,
+            {"visit": CoreSWHID(object_type=ObjectType.SNAPSHOT, object_id=_x(HASH))},
+            f"swh:1:cnt:{HASH};visit=swh:1:snp:{HASH}",
+        ),
+        (ObjectType.CONTENT, {"visit": 42}, TypeError),
+        (ObjectType.CONTENT, {"visit": f"swh:1:rel:{HASH}"}, ValidationError,),
+        (
+            ObjectType.CONTENT,
+            {"visit": CoreSWHID(object_type=ObjectType.RELEASE, object_id=_x(HASH))},
+            ValidationError,
+        ),
+        # anchor:
+        (
+            ObjectType.CONTENT,
+            {"anchor": f"swh:1:snp:{HASH}"},
+            f"swh:1:cnt:{HASH};anchor=swh:1:snp:{HASH}",
+        ),
+        (
+            ObjectType.CONTENT,
+            {"anchor": CoreSWHID(object_type=ObjectType.SNAPSHOT, object_id=_x(HASH))},
+            f"swh:1:cnt:{HASH};anchor=swh:1:snp:{HASH}",
+        ),
+        (
+            ObjectType.CONTENT,
+            {"anchor": f"swh:1:dir:{HASH}"},
+            f"swh:1:cnt:{HASH};anchor=swh:1:dir:{HASH}",
+        ),
+        (
+            ObjectType.CONTENT,
+            {"anchor": CoreSWHID(object_type=ObjectType.DIRECTORY, object_id=_x(HASH))},
+            f"swh:1:cnt:{HASH};anchor=swh:1:dir:{HASH}",
+        ),
+        (ObjectType.CONTENT, {"anchor": 42}, TypeError),
+        (ObjectType.CONTENT, {"anchor": f"swh:1:cnt:{HASH}"}, ValidationError,),
+        (
+            ObjectType.CONTENT,
+            {"anchor": CoreSWHID(object_type=ObjectType.CONTENT, object_id=_x(HASH))},
+            ValidationError,
+        ),
+        # path:
+        (ObjectType.CONTENT, {"path": b"/foo"}, f"swh:1:cnt:{HASH};path=/foo",),
+        (
+            ObjectType.CONTENT,
+            {"path": b"/foo;bar"},
+            f"swh:1:cnt:{HASH};path=/foo%3Bbar",
+        ),
+        (ObjectType.CONTENT, {"path": "/foo"}, f"swh:1:cnt:{HASH};path=/foo",),
+        (
+            ObjectType.CONTENT,
+            {"path": "/foo;bar"},
+            f"swh:1:cnt:{HASH};path=/foo%3Bbar",
+        ),
+        (ObjectType.CONTENT, {"path": 42}, Exception),
+        # lines:
+        (ObjectType.CONTENT, {"lines": (42, None)}, f"swh:1:cnt:{HASH};lines=42",),
+        (ObjectType.CONTENT, {"lines": (21, 42)}, f"swh:1:cnt:{HASH};lines=21-42",),
+        (ObjectType.CONTENT, {"lines": 42}, TypeError,),
+        (ObjectType.CONTENT, {"lines": (None, 42)}, ValueError,),
+        (ObjectType.CONTENT, {"lines": ("42", None)}, ValueError,),
+    ],
+)
+def test_QualifiedSWHID_init(object_type, qualifiers, expected):
+    """Tests validation and converters of qualifiers"""
+    if isinstance(expected, type):
+        assert issubclass(expected, Exception)
+        with pytest.raises(expected):
+            QualifiedSWHID(object_type=object_type, object_id=_x(HASH), **qualifiers)
+    else:
+        assert isinstance(expected, str)
+        swhid = QualifiedSWHID(
+            object_type=object_type, object_id=_x(HASH), **qualifiers
+        )
+
+        # Check the build object has the right serialization
+        assert expected == str(swhid)
+
+        # Check the internal state of the object is the same as if parsed from a string
+        assert QualifiedSWHID.from_string(expected) == swhid
+
+
 def test_QualifiedSWHID_hash():
     object_id = _x("94a9ed024d3859793618152ea559a168bbcbb5e2")