Check loop.qnt's properties against the real loop (M2.1, PR D part 1)

test_loop_properties.py walks the new loop with a seeded mix of operator
and Gitea actions (go-aheads, stale go-aheads, answers, comments, merges,
the comment-then-merge race, closes, abandon, a crash and restart) and an
adaptive scripted model, checking every loop.qnt property after every
step. It found two bugs, both fixed with regression tests: abandoning an
item left its open PR open (the model's fix 1, now in code), and after a
review fix became a follow-up PR, the next fix went to the merged branch.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/tests/test_loop_milestones.py

@@ -96,6 +96,9 @@ class Forge:
     def close_issue(self, repo: str, index: int) -> None:
         self.closed_issues.append(index)
 
+    def close_pull_request(self, repo: str, index: int) -> None:
+        self.prs[index]["state"] = "closed"
+
     # what the operator does in Gitea
     def merge(self, n: int) -> None:
         head = self.prs[n]["head"]
@@ -429,3 +432,45 @@ def test_boot_asks_when_a_publish_never_reached_gitea(world: dict[str, Any]) ->
     assert store.pending_intents() == []
     assert loop_of(item(world)).wait == ANSWER
     assert "publishing was cut off by a restart" in transport.outbound[-1].text
+
+
+def test_a_fix_after_a_follow_up_pr_goes_to_the_follow_up(
+    world: dict[str, Any],
+) -> None:
+    # Found by the property walk (seed 7): after a fix became a follow-up PR,
+    # the next fix was pushed to the original, merged branch and lost.
+    forge: Forge = world["forge"]
+    model = ScriptedModel(
+        RESTATE,
+        WORK + FINISH,
+        [call("write_file", path="fix1.py", content="a = 1\n"), *FINISH],
+        [call("write_file", path="fix2.py", content="b = 2\n"), *FINISH],
+    )
+    agent, transport = loop_agent(world, model)
+    agent.intake()
+    say(transport, world, "go")
+    [first] = forge.prs
+    forge.comments[first] = [Comment(1, "don", "add fix1", "t")]
+    agent.watch()
+    forge.merge(first)  # merged before the fix lands: a follow-up PR
+    agent._schedule()
+    follow = loop_of(item(world)).pr
+    assert follow != first
+    forge.comments[follow] = [Comment(2, "don", "add fix2", "t")]
+    agent.watch()
+    agent._schedule()
+    assert len(forge.prs) == 2  # pushed to the follow-up, not a third PR
+    assert "fix2.py" in forge.files(follow)
+
+
+def test_abandoning_an_item_closes_its_open_pr(world: dict[str, Any]) -> None:
+    # Found by the property walk (seed 4); the model's fix 1 (L2).
+    forge: Forge = world["forge"]
+    agent, transport = loop_agent(world, ScriptedModel(RESTATE, WORK + FINISH))
+    agent.intake()
+    say(transport, world, "go")
+    [pr] = forge.prs
+    say(transport, world, "abandon")
+    assert item(world).outcome == "abandoned"
+    assert forge.prs[pr]["state"] == "closed"
+    assert (pr, "abandoned: abandoned by @don:test") in forge.posted