diff --git a/skltemplate/utils/tests/test_discovery.py b/skltemplate/utils/tests/test_discovery.py
index 2be0f0c..a78c029 100644
--- a/skltemplate/utils/tests/test_discovery.py
+++ b/skltemplate/utils/tests/test_discovery.py
@@ -1,6 +1,8 @@
 # Authors: scikit-learn-contrib developers
 # License: BSD 3 clause
 
+import pytest
+
 from skltemplate.utils.discovery import all_displays, all_estimators, all_functions
 
 
@@ -8,6 +10,16 @@ def test_all_estimators():
     estimators = all_estimators()
     assert len(estimators) == 3
 
+    estimators = all_estimators(type_filter="classifier")
+    assert len(estimators) == 1
+
+    estimators = all_estimators(type_filter=["classifier", "transformer"])
+    assert len(estimators) == 2
+
+    err_msg = "Parameter type_filter must be"
+    with pytest.raises(ValueError, match=err_msg):
+        all_estimators(type_filter="xxxx")
+
 
 def test_all_displays():
     displays = all_displays()