diff --git a/nitransforms/base.py b/nitransforms/base.py
index 67acc073..fa05f1f6 100644
--- a/nitransforms/base.py
+++ b/nitransforms/base.py
@@ -287,6 +287,12 @@ def __len__(self):
         By default, all transforms are of length one.
         This must be overriden by transforms arrays and chains.
 
+        Example
+        -------
+        >>> T1 = TransformBase()
+        >>> len(T1)
+        1
+
         """
         return 1
 
diff --git a/nitransforms/tests/test_base.py b/nitransforms/tests/test_base.py
index 4bb147fd..49d7f7af 100644
--- a/nitransforms/tests/test_base.py
+++ b/nitransforms/tests/test_base.py
@@ -198,3 +198,18 @@ def test_SurfaceMesh(testdata_path):
 
     with pytest.raises(TypeError):
         SurfaceMesh(nb.load(shape_path))
+
+
+def test_apply_deprecation(monkeypatch):
+    """Make sure a deprecation warning is issued."""
+    from nitransforms import resampling
+
+    def _retval(*args, **kwargs):
+        return 1
+
+    monkeypatch.setattr(resampling, "apply", _retval)
+
+    with pytest.deprecated_call():
+        retval = TransformBase().apply()
+
+    assert retval == 1