bpo-42213: Remove redundant cyclic GC hack in sqlite3 (GH-26517)

The sqlite3 module now fully implements the GC protocol, so there's no
need for this workaround anymore.

- Add and use managed resource helper for connections using TESTFN
- Sort test imports
- Split open-tests into their own test case

Automerge-Triggered-By: GH:vstinner

Lib/sqlite3/test/dbapi.py

@@ -20,14 +20,26 @@
 #    misrepresented as being the original software.
 # 3. This notice may not be removed or altered from any source distribution.
 
-import threading
-import unittest
+import contextlib
 import sqlite3 as sqlite
 import sys
+import threading
+import unittest
 
 from test.support.os_helper import TESTFN, unlink
 
 
+# Helper for tests using TESTFN
+@contextlib.contextmanager
+def managed_connect(*args, **kwargs):
+    cx = sqlite.connect(*args, **kwargs)
+    try:
+        yield cx
+    finally:
+        cx.close()
+        unlink(TESTFN)
+
+
 class ModuleTests(unittest.TestCase):
     def test_api_level(self):
         self.assertEqual(sqlite.apilevel, "2.0",
@@ -190,26 +202,27 @@ class ConnectionTests(unittest.TestCase):
         with self.assertRaises(AttributeError):
             self.cx.in_transaction = True
 
+class OpenTests(unittest.TestCase):
+    _sql = "create table test(id integer)"
+
     def test_open_with_path_like_object(self):
         """ Checks that we can successfully connect to a database using an object that
             is PathLike, i.e. has __fspath__(). """
-        self.addCleanup(unlink, TESTFN)
         class Path:
             def __fspath__(self):
                 return TESTFN
         path = Path()
-        with sqlite.connect(path) as cx:
-            cx.execute('create table test(id integer)')
+        with managed_connect(path) as cx:
+            cx.execute(self._sql)
 
     def test_open_uri(self):
-        self.addCleanup(unlink, TESTFN)
-        with sqlite.connect(TESTFN) as cx:
-            cx.execute('create table test(id integer)')
-        with sqlite.connect('file:' + TESTFN, uri=True) as cx:
-            cx.execute('insert into test(id) values(0)')
-        with sqlite.connect('file:' + TESTFN + '?mode=ro', uri=True) as cx:
-            with self.assertRaises(sqlite.OperationalError):
-                cx.execute('insert into test(id) values(1)')
+        with managed_connect(TESTFN) as cx:
+            cx.execute(self._sql)
+        with managed_connect(f"file:{TESTFN}", uri=True) as cx:
+            cx.execute(self._sql)
+        with self.assertRaises(sqlite.OperationalError):
+            with managed_connect(f"file:{TESTFN}?mode=ro", uri=True) as cx:
+                cx.execute(self._sql)
 
 
 class CursorTests(unittest.TestCase):