diff --git a/ndfilters/tests/__init__.py b/ndfilters/_tests/__init__.py
similarity index 100%
rename from ndfilters/tests/__init__.py
rename to ndfilters/_tests/__init__.py
diff --git a/ndfilters/tests/test_trimmed_mean.py b/ndfilters/_tests/test_trimmed_mean.py
similarity index 93%
rename from ndfilters/tests/test_trimmed_mean.py
rename to ndfilters/_tests/test_trimmed_mean.py
index fa6f631..dc3a21f 100644
--- a/ndfilters/tests/test_trimmed_mean.py
+++ b/ndfilters/_tests/test_trimmed_mean.py
@@ -8,14 +8,14 @@
 @pytest.mark.parametrize(
     argnames="array",
     argvalues=[
-        np.random.random(16),
-        np.random.random((16, 17)),
-        np.random.random((16, 17, 18)),
+        np.random.random(5),
+        np.random.random((5, 6)),
+        np.random.random((5, 6, 7)),
     ],
 )
 @pytest.mark.parametrize(
     argnames="kernel_shape",
-    argvalues=[5, (5,), (5, 6), (5, 6, 7)],
+    argvalues=[2, (3,), (3, 4), (3, 4, 5)],
 )
 @pytest.mark.parametrize(
     argnames="axis",