test: a request that raises is rolled back, as production rolls it back

The shared test session kept whatever a failing handler flushed and never
committed, so a later read in the test saw a write production loses when
get_db closes the session — and a handler whose failure path must commit
(E16: the tracker's issue link) looked right without the commit.

backend/tests/conftest.py

@@ -111,8 +111,11 @@ def _request_dep(db, unfinished: list[str]):
     request that ends normally with a write it did not commit — flushed, or still only staged — is
     recorded, and the test fails on it at teardown. Only the ROOT transaction's end clears it: a
     savepoint released inside the handler commits nothing. The test's own staged rows are flushed before the request starts — they are the
-    test's business, not the handler's. A request that raises is exempt: its writes are meant to
+    test's business, not the handler's. A request that raises is rolled back, as production's
-    roll back."""
+    `close()` rolls it back: without that, what a failing handler flushed but never committed stayed
+    readable to the rest of the test — the one state production cannot be in (E16: an issue created
+    on the tracker before a failed upload was kept only by an explicit commit, and nothing saw it
+    missing)."""
 
     def dep(conn: HTTPConnection):
         db.flush()
@@ -133,6 +136,9 @@ def _request_dep(db, unfinished: list[str]):
             staged = db.new or db.deleted or any(db.is_modified(o) for o in db.dirty)
             if state["dirty"] or staged:
                 unfinished.append(f"{conn.scope.get('method', 'WS')} {conn.url.path}")
+        except Exception:
+            db.rollback()
+            raise
         finally:
             for name, fn in hooks:
                 event.remove(db, name, fn)

backend/tests/test_override_dep_convention.py

@@ -58,3 +58,27 @@ def test_the_commit_check_counts_only_the_root_transaction(db):
         next(request)
     assert db.info["unfinished"] == ["POST /probe"]
     db.info["unfinished"].clear()  # recorded as it should be — not this test's failure
+
+
+def test_a_request_that_raises_leaves_nothing_it_did_not_commit(db):
+    """Production closes a failing request's session, which rolls back whatever it flushed and did
+    not commit; the shared test session must do the same, or a later read in the test sees a write
+    production would have lost (E16: the tracker's issue link, kept only by an explicit commit in
+    the handler's failure path). Driven directly, as a request would drive the dependency."""
+    import pytest
+    from sqlalchemy import select
+    from starlette.requests import HTTPConnection
+
+    from app.models import User
+
+    conn = HTTPConnection(
+        {"type": "http", "method": "POST", "path": "/probe", "headers": [], "query_string": b""}
+    )
+    request = db.info["request"](conn)
+    session = next(request)
+    session.add(User(email="rolled-back-probe@example.com"))
+    session.flush()
+    with pytest.raises(RuntimeError):
+        request.throw(RuntimeError("the handler failed"))
+    assert db.scalar(select(User).where(User.email == "rolled-back-probe@example.com")) is None
+    assert db.info["unfinished"] == []  # a failing request is rolled back, not reported