ansicht der verbundenen kassenbücher an der kategorie + test

tests/test_category.py

@@ -78,6 +78,9 @@ class CategoryTestCase(CashbookTestCase):
             self.assertEqual(len(book.categories), 1)
             self.assertEqual(book.categories[0].rec_name, 'Cat 0')
 
+            self.assertEqual(len(category.cashbooks), 1)
+            self.assertEqual(category.cashbooks[0].rec_name, 'Book 1 | 0.00 usd | Open')
+
             # replace category
             Book.write(*[
                 [book],