pythongh-108558: Improve sqlite3 row factory tests (python#108578)

Add test_sqlite_row_keys() to explicitly test sqlite3.Row.keys().

Cleanups:
- Reduce test noise by converting docstrings to regular comments
- Reduce boilerplate code by adding a setUp() method to RowFactoryTests

Co-authored-by: Erlend E. Aasland <erlend@python.org>

Lib/test/test_sqlite3/test_factory.py

@@ -116,13 +116,16 @@ def test_is_produced_by_factory(self):
 
 class RowFactoryTests(MemoryDatabaseMixin, unittest.TestCase):
 
+    def setUp(self):
+        super().setUp()
+        self.con.row_factory = sqlite.Row
+
     def test_custom_factory(self):
         self.con.row_factory = lambda cur, row: list(row)
         row = self.con.execute("select 1, 2").fetchone()
         self.assertIsInstance(row, list)
 
     def test_sqlite_row_index(self):
-        self.con.row_factory = sqlite.Row
         row = self.con.execute("select 1 as a_1, 2 as b").fetchone()
         self.assertIsInstance(row, sqlite.Row)
 
@@ -153,7 +156,6 @@ def test_sqlite_row_index(self):
             row[complex()]  # index must be int or string
 
     def test_sqlite_row_index_unicode(self):
-        self.con.row_factory = sqlite.Row
         row = self.con.execute("select 1 as \xff").fetchone()
         self.assertEqual(row["\xff"], 1)
         with self.assertRaises(IndexError):
@@ -163,7 +165,6 @@ def test_sqlite_row_index_unicode(self):
 
     def test_sqlite_row_slice(self):
         # A sqlite.Row can be sliced like a list.
-        self.con.row_factory = sqlite.Row
         row = self.con.execute("select 1, 2, 3, 4").fetchone()
         self.assertEqual(row[0:0], ())
         self.assertEqual(row[0:1], (1,))
@@ -180,8 +181,7 @@ def test_sqlite_row_slice(self):
         self.assertEqual(row[3:0:-2], (4, 2))
 
     def test_sqlite_row_iter(self):
-        """Checks if the row object is iterable"""
-        self.con.row_factory = sqlite.Row
+        # Checks if the row object is iterable.
         row = self.con.execute("select 1 as a, 2 as b").fetchone()
 
         # Is iterable in correct order and produces valid results:
@@ -193,23 +193,20 @@ def test_sqlite_row_iter(self):
         self.assertEqual(items, [1, 2])
 
     def test_sqlite_row_as_tuple(self):
-        """Checks if the row object can be converted to a tuple"""
-        self.con.row_factory = sqlite.Row
+        # Checks if the row object can be converted to a tuple.
         row = self.con.execute("select 1 as a, 2 as b").fetchone()
         t = tuple(row)
         self.assertEqual(t, (row['a'], row['b']))
 
     def test_sqlite_row_as_dict(self):
-        """Checks if the row object can be correctly converted to a dictionary"""
-        self.con.row_factory = sqlite.Row
+        # Checks if the row object can be correctly converted to a dictionary.
         row = self.con.execute("select 1 as a, 2 as b").fetchone()
         d = dict(row)
         self.assertEqual(d["a"], row["a"])
         self.assertEqual(d["b"], row["b"])
 
     def test_sqlite_row_hash_cmp(self):
-        """Checks if the row object compares and hashes correctly"""
-        self.con.row_factory = sqlite.Row
+        # Checks if the row object compares and hashes correctly.
         row_1 = self.con.execute("select 1 as a, 2 as b").fetchone()
         row_2 = self.con.execute("select 1 as a, 2 as b").fetchone()
         row_3 = self.con.execute("select 1 as a, 3 as b").fetchone()
@@ -242,21 +239,24 @@ def test_sqlite_row_hash_cmp(self):
         self.assertEqual(hash(row_1), hash(row_2))
 
     def test_sqlite_row_as_sequence(self):
-        """ Checks if the row object can act like a sequence """
-        self.con.row_factory = sqlite.Row
+        # Checks if the row object can act like a sequence.
         row = self.con.execute("select 1 as a, 2 as b").fetchone()
 
         as_tuple = tuple(row)
         self.assertEqual(list(reversed(row)), list(reversed(as_tuple)))
         self.assertIsInstance(row, Sequence)
 
+    def test_sqlite_row_keys(self):
+        # Checks if the row object can return a list of columns as strings.
+        row = self.con.execute("select 1 as a, 2 as b").fetchone()
+        self.assertEqual(row.keys(), ['a', 'b'])
+
     def test_fake_cursor_class(self):
         # Issue #24257: Incorrect use of PyObject_IsInstance() caused
         # segmentation fault.
         # Issue #27861: Also applies for cursor factory.
         class FakeCursor(str):
             __class__ = sqlite.Cursor
-        self.con.row_factory = sqlite.Row
         self.assertRaises(TypeError, self.con.cursor, FakeCursor)
         self.assertRaises(TypeError, sqlite.Row, FakeCursor(), ())