add default exceptions to relations, test one argument, test querysetproxy, test deeply nested

tests/test_relations_default_exception.py

@@ -0,0 +1,65 @@
+# type: ignore
+from typing import List, Optional
+
+import databases
+import pytest
+import sqlalchemy
+
+import ormar
+from ormar.exceptions import ModelDefinitionError
+from tests.settings import DATABASE_URL
+
+database = databases.Database(DATABASE_URL, force_rollback=True)
+metadata = sqlalchemy.MetaData()
+
+
+class Author(ormar.Model):
+    class Meta:
+        tablename = "authors"
+        database = database
+        metadata = metadata
+
+    id: int = ormar.Integer(primary_key=True)
+    first_name: str = ormar.String(max_length=80)
+    last_name: str = ormar.String(max_length=80)
+
+
+class Category(ormar.Model):
+    class Meta:
+        tablename = "categories"
+        database = database
+        metadata = metadata
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=40)
+
+
+def test_fk_error():
+    with pytest.raises(ModelDefinitionError):
+
+        class Post(ormar.Model):
+            class Meta:
+                tablename = "posts"
+                database = database
+                metadata = metadata
+
+            id: int = ormar.Integer(primary_key=True)
+            title: str = ormar.String(max_length=200)
+            categories: Optional[List[Category]] = ormar.ManyToMany(Category)
+            author: Optional[Author] = ormar.ForeignKey(Author, default="aa")
+
+
+def test_m2m_error():
+    with pytest.raises(ModelDefinitionError):
+
+        class Post(ormar.Model):
+            class Meta:
+                tablename = "posts"
+                database = database
+                metadata = metadata
+
+            id: int = ormar.Integer(primary_key=True)
+            title: str = ormar.String(max_length=200)
+            categories: Optional[List[Category]] = ormar.ManyToMany(
+                Category, default="aa"
+            )