Clarify ensure_autocommit_off() autocommit behavior

sqlite_utils/db.py

@@ -403,14 +403,18 @@ def close(self) -> None:
     @contextlib.contextmanager
     def ensure_autocommit_off(self) -> Generator[None, None, None]:
         """
-        Ensure autocommit is off for this database connection.
+        Ensure autocommit is on for this database connection.
+
+        Despite the historical method name, this temporarily sets
+        ``self.conn.isolation_level = None`` so statements execute in autocommit
+        mode inside the block.
 
         Example usage::
 
             with db.ensure_autocommit_off():
                 # do stuff here
 
-        This will reset to the previous autocommit state at the end of the block.
+        This will reset to the previous isolation level at the end of the block.
         """
         old_isolation_level = self.conn.isolation_level
         try:

tests/test_wal.py

@@ -21,3 +21,11 @@ def test_enable_disable_wal(db_path_tmpdir):
     db.disable_wal()
     assert "delete" == db.journal_mode
     assert "test.db-wal" not in [f.basename for f in tmpdir.listdir()]
+
+
+def test_ensure_autocommit_off_sets_autocommit_mode_temporarily(db_path_tmpdir):
+    db, path, tmpdir = db_path_tmpdir
+    original_isolation_level = db.conn.isolation_level
+    with db.ensure_autocommit_off():
+        assert db.conn.isolation_level is None
+    assert db.conn.isolation_level == original_isolation_level