diff --git a/src/wabot/pacing.py b/src/wabot/pacing.py
index c32c16b..852ef0d 100644
--- a/src/wabot/pacing.py
+++ b/src/wabot/pacing.py
@@ -11,7 +11,12 @@ import random
 
 
 class NoPacing:
-    """Instant actions, exact clicks."""
+    """Instant actions, exact clicks.
+
+    Also the base class for custom pacing policies; do not use
+    ``isinstance(x, NoPacing)`` to test whether pacing is disabled —
+    HumanPacing subclasses this.
+    """
 
     def delay(self, action: str) -> float:
         """Seconds to sleep before performing ``action``."""
diff --git a/tests/unit/test_pacing.py b/tests/unit/test_pacing.py
index 5800f62..a4981fe 100644
--- a/tests/unit/test_pacing.py
+++ b/tests/unit/test_pacing.py
@@ -24,15 +24,21 @@ class TestHumanPacing:
     def test_unknown_action_has_no_delay(self):
         assert HumanPacing().delay("unknown-action") == 0.0
 
+    def test_delays_actually_vary(self):
+        assert len({HumanPacing().delay("text") for _ in range(50)}) > 1
+
     def test_click_offset_stays_inside_element(self):
         p = HumanPacing()
+        offsets = []
         for _ in range(200):
             offset = p.click_offset(100, 40)
             assert offset is not None
+            offsets.append(offset)
             x, y = offset
             # offsets are measured from the element CENTER (selenium 4)
             assert -49 <= x <= 49
             assert -19 <= y <= 19
+        assert any(o != (0, 0) for o in offsets)
 
     def test_tiny_elements_get_plain_click(self):
         p = HumanPacing()