Better test coverage in database wrapper.

matemat/db/test/test_wrapper.py

@@ -103,3 +103,20 @@ class DatabaseTest(unittest.TestCase):
             with db.transaction():
                 with self.assertRaises(RuntimeError):
                     self.db.close()
+
+    def test_use_before_open(self):
+        with self.assertRaises(RuntimeError):
+            with self.db.transaction():
+                pass
+        with self.assertRaises(RuntimeError):
+            self.db.close()
+        with self.assertRaises(RuntimeError):
+            _ = self.db._user_version
+        with self.assertRaises(RuntimeError):
+            self.db._user_version = 42
+
+    def test_setup_prevent_downgrade(self):
+        self.db._sqlite_db = sqlite3.connect(':memory:')
+        self.db._user_version = 1337
+        with self.assertRaises(RuntimeError):
+            self.db._setup()