Add transactional test fixture, change functions to use it

tests/test_database.py

@@ -16,24 +16,40 @@ def db_session() -> db.dal.Session:
         db.dal.engine.pool.recreate()
 
 
+@fixture(scope='function')
+def session(db_session) -> db.dal.Session:
+    """Provides a transactional scope around each test."""
+    connection = db_session.connection()
+    transaction = connection.begin()
+
+    # bind the session to this specific connection
+    db_session.bind = connection
+
+    yield db_session
+
+    # roll all changed that occurred back
+    transaction.rollback()
+    connection.close()
+
+
 def test_base() -> None:
     """Test to ensure db.Base() is a sqlalchemy DeclarativeBase object."""
     assert isinstance(db.Base(), sqlalchemy.orm.DeclarativeBase)
 
 
-def test_powerball_draw_by_date_blank(db_session) -> None:
+def test_powerball_draw_by_date_blank(session) -> None:
     """
         Test that a null record is returned when no date is provided and that no dateless
         records can exist in the table.
     """
-    with db_session as session:
+    with session:
         blank_results = session.query(db.PowerballDraw).filter_by(draw_date='').all()
         assert blank_results == []
 
 
-def test_powerball_draw_by_date(db_session) -> None:
+def test_powerball_draw_by_date(session) -> None:
     """Test to be sure we can find the first draw in the table by date."""
-    with db_session as session:
+    with session:
         date = datetime(2010, 2, 3).date()
         draw = db.PowerballDraw(draw_date=date, main_ball1=17, main_ball2=22, main_ball3=36, main_ball4=37,
              main_ball5=52, powerball=24, power_play=2)
@@ -42,9 +58,9 @@ def test_powerball_draw_by_date(db_session) -> None:
         assert record == draw
 
 
-def test_powerball_draw_integrity(db_session) -> None:
+def test_powerball_draw_integrity(session) -> None:
     """Test that a proper error is received when a duplicate value insertion is attempted."""
-    with db_session as session:
+    with session:
         date = datetime.strptime('02/03/2010','%m/%d/%Y').date()
         draw = db.PowerballDraw(draw_date=date, main_ball1=17, main_ball2=22, main_ball3=36, main_ball4=37,
                 main_ball5=52, powerball=24, power_play=2)
@@ -59,9 +75,9 @@ def test_powerball_draw_integrity(db_session) -> None:
             session.close()
 
 
-def test_powerball_repr_and_str(db_session) -> None:
+def test_powerball_repr_and_str(session) -> None:
     """Test the __repr__ and __str__ methods of PowerballDraw objects."""
-    with db_session as session:
+    with session:
         date = datetime(2010, 2, 3).date()
         record = session.query(db.PowerballDraw).filter_by(draw_date=date).first()
         assert str(record) == '2010-02-03, [17, 22, 36, 37, 52], 24, 2x'