diff --git a/src/hyperactive/_registry/__init__.py b/src/hyperactive/registry/__init__.py
similarity index 50%
rename from src/hyperactive/_registry/__init__.py
rename to src/hyperactive/registry/__init__.py
index 722edf23..4216d6d0 100644
--- a/src/hyperactive/_registry/__init__.py
+++ b/src/hyperactive/registry/__init__.py
@@ -1,5 +1,5 @@
 """Hyperactive registry."""
 
-from hyperactive._registry._lookup import all_objects
+from hyperactive.registry._lookup import all_objects
 
 __all__ = ["all_objects"]
diff --git a/src/hyperactive/_registry/_lookup.py b/src/hyperactive/registry/_lookup.py
similarity index 94%
rename from src/hyperactive/_registry/_lookup.py
rename to src/hyperactive/registry/_lookup.py
index 63f23b07..2410468f 100644
--- a/src/hyperactive/_registry/_lookup.py
+++ b/src/hyperactive/registry/_lookup.py
@@ -34,6 +34,16 @@ def all_objects(
     Not included are: the base classes themselves, classes defined in test
     modules.
 
+    To filter by object type, use the ``object_types`` parameter:
+
+    * ``"optimizer"``: optimizers, e.g., the Hill Climbing optimizer,
+      or the Particle Swarm optimizer
+    * ``"experiment"``: experiments, e.g., the Ackley function, or an ``sklearn``
+      cross-validation experiment
+    * if ``None``, no filter is applied and all objects are returned.
+
+    To filter by tag, use the ``filter_tags`` parameter.
+
     Parameters
     ----------
     object_types: str, list of str, optional (default=None)
@@ -137,7 +147,7 @@ def all_objects(
 
     Examples
     --------
-    >>> from hyperactive._registry import all_objects
+    >>> from hyperactive.registry import all_objects
     >>> # return a complete list of objects as pd.Dataframe
     >>> all_objects(as_dataframe=True)  # doctest: +SKIP
 
diff --git a/src/hyperactive/registry/tests/__init__.py b/src/hyperactive/registry/tests/__init__.py
new file mode 100644
index 00000000..96b5c8c8
--- /dev/null
+++ b/src/hyperactive/registry/tests/__init__.py
@@ -0,0 +1 @@
+"""Registry tests."""
diff --git a/src/hyperactive/registry/tests/test_lookup.py b/src/hyperactive/registry/tests/test_lookup.py
new file mode 100644
index 00000000..44cb6241
--- /dev/null
+++ b/src/hyperactive/registry/tests/test_lookup.py
@@ -0,0 +1,52 @@
+# copyright: hyperactive developers, BSD-3-Clause License (see LICENSE file)
+"""Testing of registry lookup functionality."""
+
+# based on the sktime module of same name
+
+__author__ = ["fkiraly"]
+
+import pytest
+
+from hyperactive.registry import all_objects
+
+object_types = ["optimizer", "experiment"]
+
+
+def _to_list(obj):
+    """Put obj in list if it is not a list."""
+    if not isinstance(obj, list):
+        return [obj]
+    else:
+        return obj.copy()
+
+
+@pytest.mark.parametrize("return_names", [True, False])
+@pytest.mark.parametrize("object_type", object_types)
+def test_all_objects_by_scitype(object_type, return_names):
+    """Check that all_objects return argument has correct type."""
+    objects = all_objects(
+        object_types=object_type,
+        return_names=return_names,
+    )
+
+    assert isinstance(objects, list)
+    # there should be at least one object returned
+    assert len(objects) > 0
+
+    # checks return type specification (see docstring)
+    for obj in objects:
+        if return_names:
+            assert isinstance(obj, tuple) and len(obj) == 2
+            name = obj[0]
+            obj_cls = obj[1]
+            assert isinstance(name, str)
+            assert hasattr(obj_cls, "__name__")
+            assert name == obj_cls.__name__
+        else:
+            obj_cls = obj
+
+        assert hasattr(obj_cls, "get_tags")
+        type_from_obj = obj_cls.get_class_tag("object_type")
+        type_from_obj = _to_list(type_from_obj)
+
+        assert object_type in type_from_obj
diff --git a/src/hyperactive/tests/test_all_objects.py b/src/hyperactive/tests/test_all_objects.py
index 986c0086..606ff43a 100644
--- a/src/hyperactive/tests/test_all_objects.py
+++ b/src/hyperactive/tests/test_all_objects.py
@@ -7,7 +7,7 @@
 from skbase.testing import QuickTester as _QuickTester
 from skbase.testing import TestAllObjects as _TestAllObjects
 
-from hyperactive._registry import all_objects
+from hyperactive.registry import all_objects
 from hyperactive.tests._config import EXCLUDE_ESTIMATORS, EXCLUDED_TESTS
 from hyperactive.tests._doctest import run_doctest