remove unneeded tests, document derive

crates/bevy_ecs/src/entity/visit_entities.rs

@@ -42,6 +42,24 @@ where
 ///
 /// It may be useful to implement directly for types that can't produce an
 /// iterator for lifetime reasons, such as those involving internal mutexes.
+///
+/// This trait is derivable for structs via `#[derive(IterEntities)]`. Fields
+/// not containing entities can be ignored with `#[iter_entities(ignore)]`.
+///
+/// # Example
+///
+/// ```rust
+/// # use bevy_ecs::entity::{Entity, IterEntities};
+/// # use bevy_utils::hashbrown::HashSet;
+/// #[derive(IterEntities)]
+/// struct MyEntities {
+///     lots: Vec<Entity>,
+///     one: Entity,
+///     maybe: Option<Entity>,
+///     #[iter_entities(ignore)]
+///     not_an_entity: String,
+/// }
+/// ```
 pub trait IterEntities {
     /// Get an iterator over contained entities.
     fn iter_entities(&self) -> impl Iterator<Item = Entity>;

crates/bevy_ecs/src/lib.rs

@@ -2053,7 +2053,8 @@ mod tests {
     #[derive(Component, IterEntities)]
     struct MyEntities {
         entities: Vec<Entity>,
-        entities2: Vec<Entity>,
+        another_one: Entity,
+        maybe_entity: Option<Entity>,
         #[iter_entities(ignore)]
         something_else: String,
     }

crates/bevy_hierarchy/src/components/children.rs

@@ -160,17 +160,3 @@ impl<'a> IntoIterator for &'a Children {
         self.0.iter()
     }
 }
-
-#[cfg(test)]
-mod test {
-    use bevy_ecs::entity::VisitEntities;
-
-    use super::*;
-
-    fn assert_impls_map_entities<M: VisitEntities>() {}
-
-    #[test]
-    fn children_impls_map_entities() {
-        assert_impls_map_entities::<Children>();
-    }
-}

crates/bevy_window/src/window.rs

@@ -1219,19 +1219,8 @@ pub struct ClosingWindow;
 
 #[cfg(test)]
 mod tests {
-    use bevy_ecs::entity::VisitEntities;
-
     use super::*;
 
-    // Compile-time assertion that a type implements MapEntitiesMut
-    fn impl_map_entities<M: VisitEntities>() {}
-
-    // Ensure that WidowRef implements MapEntitiesMut
-    #[test]
-    fn window_impls_map_entities() {
-        impl_map_entities::<WindowRef>();
-    }
-
     // Checks that `Window::physical_cursor_position` returns the cursor position if it is within
     // the bounds of the window.
     #[test]