diff --git a/01.workspace/heave/src/tst/intended_use.rs b/01.workspace/heave/src/tst/intended_use.rs
index db5f2a1..e9b9f97 100644
--- a/01.workspace/heave/src/tst/intended_use.rs
+++ b/01.workspace/heave/src/tst/intended_use.rs
@@ -21,4 +21,44 @@ mod tests {
         assert_eq!(name, Some(&Value::Text(String::from("laptop"))));
         assert_eq!(price, Some(&Value::UnsignedInt(200000)));
     }
+    #[test]
+    fn check_003() {
+        // Demonstrate attribute value setting
+        let mut product = Entity::new("product");
+        // new product
+        product.set("price", 200000u64);
+        // set price
+        let price = product.value_of("price");
+        assert_eq!(price, Some(&Value::UnsignedInt(200000)));
+        // set in stock
+        product.set("in_stock", true);
+        let in_stock = product.value_of("in_stock");
+        assert_eq!(in_stock, Some(&Value::Bool(true)));
+        // set in stock again
+        let prev_in_stock = product.set("in_stock", false);
+        let in_stock = product.value_of("in_stock");
+        assert_eq!(prev_in_stock, Some(Value::Bool(true)));
+        assert_eq!(in_stock, Some(&Value::Bool(false)));
+    }
+    #[test]
+    fn check_004() {
+        // new entities
+        let product = Entity::new("product");
+        let category = Entity::new("category");
+        // id clones for testing purposes
+        let product_id = product.id.clone();
+        let category_id = category.id.clone();
+        // new relation as entity
+        let product_has_category = Entity::new("product_has_category")
+            .with_attribute("product", product)
+            .with_attribute("category", category);
+        assert_eq!(
+            product_has_category.value_of("product"),
+            Some(&Value::Text(product_id))
+        );
+        assert_eq!(
+            product_has_category.value_of("category"),
+            Some(&Value::Text(category_id))
+        );
+    }
 }