implement unique constraint checking

test/test_db.py

@@ -3,6 +3,7 @@ from tinydb.storages import MemoryStorage
 
 from grung import examples
 from grung.db import GrungDB
+from grung.exceptions import UniqueConstraintError
 
 
 @pytest.fixture
@@ -49,3 +50,13 @@ def test_crud(db):
     # delete
     db.delete(players)
     assert len(db.Group) == 0
+
+
+def test_unique(db):
+    user1 = examples.User(name="john", email="john@foo")
+    user2 = examples.User(name="john", email="john@foo")
+
+    user1 = db.save(user1)
+    with pytest.raises(UniqueConstraintError):
+        user2 = db.save(user2)
+    db.save(user1)