Make systems in tests fallible

Author: Pascualex

crates/bevy_ecs/src/system/system_registry.rs

@@ -651,6 +651,18 @@ mod tests {
         assert_eq!(output, NonCopy(3));
     }
 
+    #[test]
+    fn fallible_system() {
+        fn four() -> Result<i32> {
+            Ok(4)
+        }
+
+        let mut world = World::new();
+        let fallible_system_id = world.register_system(four);
+        let output = world.run_system(fallible_system_id);
+        assert!(matches!(output, Ok(Ok(x)) if x == four().unwrap() ));
+    }
+
     #[test]
     fn exclusive_system() {
         let mut world = World::new();
@@ -751,19 +763,53 @@ mod tests {
         assert!(matches!(output, Ok(x) if x == four()));
     }
 
+    #[test]
+    fn cached_fallible_system() {
+        fn four() -> Result<i32> {
+            Ok(4)
+        }
+
+        let mut world = World::new();
+        let fallible_system_id = world.register_system_cached(four);
+        let output = world.run_system(fallible_system_id);
+        assert!(matches!(output, Ok(Ok(x)) if x == four().unwrap()));
+        let output = world.run_system_cached(four);
+        assert!(matches!(output, Ok(Ok(x)) if x == four().unwrap()));
+        let output = world.run_system_cached_with(four, ());
+        assert!(matches!(output, Ok(Ok(x)) if x == four().unwrap()));
+    }
+
     #[test]
     fn cached_system_commands() {
-        fn sys(mut counter: ResMut<Counter>) {
-            counter.0 = 1;
+        fn increase(mut counter: ResMut<Counter>) {
+            counter.0 += 1;
         }
 
         let mut world = World::new();
         world.insert_resource(Counter(0));
-
-        world.commands().run_system_cached(sys);
+        world.commands().run_system_cached(increase);
+        world.flush_commands();
+        assert_eq!(world.resource::<Counter>().0, 1);
+        world.commands().run_system_cached_with(increase, ());
         world.flush_commands();
+        assert_eq!(world.resource::<Counter>().0, 2);
+    }
 
+    #[test]
+    fn cached_fallible_system_commands() {
+        fn increase(mut counter: ResMut<Counter>) -> Result {
+            counter.0 += 1;
+            Ok(())
+        }
+
+        let mut world = World::new();
+        world.insert_resource(Counter(0));
+        world.commands().run_system_cached(increase);
+        world.flush_commands();
         assert_eq!(world.resource::<Counter>().0, 1);
+        world.commands().run_system_cached_with(increase, ());
+        world.flush_commands();
+        assert_eq!(world.resource::<Counter>().0, 2);
     }
 
     #[test]