tests/test_rule_hint_band.py

@@ -149,16 +149,29 @@ def test_shortening_a_line_does_not_decide_what_it_says_about_holding():
     precisely because the session may no longer HOLD what it was told — and
     the tail is the entire difference a reader can act on.
 
-    `compact` and `seen` are independent axes. How much room a line gets is a
+    `compact` and the ledger are independent axes. How much room a line gets is
-    fact about its rank; whether the session holds it is a fact about the
+    a fact about its rank; what the session holds is a fact about the ledger;
-    ledger; and neither may be allowed to answer the other's question.
+    and neither may be allowed to answer the other's question.
+
+    THREE STATES SINCE #4100, so this checks three. The axis grew and the test
+    grew with it — pinning only two would leave the compact branch free to
+    collapse the new middle state into either neighbour, which is the same
+    regression this was written for with one more place to hide.
     """
     rule = fake_rule(id=4, title="dev is home", when_to_apply=_TRIGGER)
-    seen = _rule_hint_line(rule, where="here", seen=True, compact=True)
     fresh = _rule_hint_line(rule, where="here", seen=False, compact=True)
-    assert seen != fresh
+    named = _rule_hint_line(rule, where="here", seen=True, compact=True)
-    assert "no longer hold it" in seen
+    held = _rule_hint_line(rule, where="here", seen=True, held=True, compact=True)
+
+    assert len({fresh, named, held}) == 3, (
+        "the compact branch collapsed two holding states into one line"
+    )
     assert "not in this session's loaded set" in fresh
+    assert "not opened" in named
+    assert "no longer hold it" in held
+    # The claim that most needs to survive shortening: a line the session never
+    # opened must not imply it did, however little room the line was given.
+    assert "no longer hold it" not in named
 
 
 def test_a_compact_line_is_materially_shorter_than_a_full_one():