Add load_one tests

src/entity/loader.rs

@@ -284,6 +284,54 @@ where
 mod tests {
     #[tokio::test]
 
+    async fn test_load_one() {
+        use crate::{
+            entity::prelude::*, tests_cfg::*, DbBackend, IntoMockRow, LoaderTrait, MockDatabase,
+        };
+
+        let db = MockDatabase::new(DbBackend::Postgres)
+            .append_query_results(vec![
+                vec![
+                    cake::Model {
+                        id: 1,
+                        name: "New York Cheese".to_owned(),
+                    }.into_mock_row(),
+                    cake::Model {
+                        id: 2,
+                        name: "London Cheese".to_owned(),
+                    }.into_mock_row()
+                ],
+            ])
+            .into_connection();
+
+        let fruits = vec![
+            fruit::Model {
+                id: 1,
+                name: "Apple".to_owned(),
+                cake_id: Some(1),
+            }
+        ];
+
+        let cakes = fruits
+            .load_one(cake::Entity::find(), &db)
+            .await
+            .expect("Should return something");
+
+        assert_eq!(
+            cakes,
+            vec![
+                Some(
+                    cake::Model {
+                        id: 1,
+                        name: "New York Cheese".to_owned(),
+                    }
+                )
+            ]
+        );
+    }
+
+    #[tokio::test]
+
     async fn test_load_many() {
         use crate::{
             entity::prelude::*, tests_cfg::*, DbBackend, IntoMockRow, LoaderTrait, MockDatabase,