bevy/tests/how_to_test_systems.rs
Alice Cecile 557ab9897a Make get_resource (and friends) infallible (#4047)
# Objective

- In the large majority of cases, users were calling `.unwrap()` immediately after `.get_resource`.
- Attempting to add more helpful error messages here resulted in endless manual boilerplate (see #3899 and the linked PRs).

## Solution

- Add an infallible variant named `.resource` and so on.
- Use these infallible variants over `.get_resource().unwrap()` across the code base.

## Notes

I did not provide equivalent methods on `WorldCell`, in favor of removing it entirely in #3939.

## Migration Guide

Infallible variants of `.get_resource` have been added that implicitly panic, rather than needing to be unwrapped.

Replace `world.get_resource::<Foo>().unwrap()` with `world.resource::<Foo>()`.

## Impact

- `.unwrap` search results before: 1084
- `.unwrap` search results after: 942
- internal `unwrap_or_else` calls added: 4
- trivial unwrap calls removed from tests and code: 146
- uses of the new `try_get_resource` API: 11
- percentage of the time the unwrapping API was used internally: 93%
2022-02-27 22:37:18 +00:00

97 lines
2.6 KiB
Rust

use bevy::prelude::*;
#[derive(Component, Default)]
struct Enemy {
hit_points: u32,
}
fn despawn_dead_enemies(mut commands: Commands, enemies: Query<(Entity, &Enemy)>) {
for (entity, enemy) in enemies.iter() {
if enemy.hit_points == 0 {
commands.entity(entity).despawn_recursive();
}
}
}
fn hurt_enemies(mut enemies: Query<&mut Enemy>) {
for mut enemy in enemies.iter_mut() {
enemy.hit_points -= 1;
}
}
fn spawn_enemy(mut commands: Commands, keyboard_input: Res<Input<KeyCode>>) {
if keyboard_input.just_pressed(KeyCode::Space) {
commands.spawn().insert(Enemy { hit_points: 5 });
}
}
#[test]
fn did_hurt_enemy() {
// Setup world
let mut world = World::default();
// Setup stage with our two systems
let mut update_stage = SystemStage::parallel();
update_stage.add_system(hurt_enemies.before("death"));
update_stage.add_system(despawn_dead_enemies.label("death"));
// Setup test entities
let enemy_id = world.spawn().insert(Enemy { hit_points: 5 }).id();
// Run systems
update_stage.run(&mut world);
// Check resulting changes
assert!(world.get::<Enemy>(enemy_id).is_some());
assert_eq!(world.get::<Enemy>(enemy_id).unwrap().hit_points, 4);
}
#[test]
fn did_despawn_enemy() {
// Setup world
let mut world = World::default();
// Setup stage with our two systems
let mut update_stage = SystemStage::parallel();
update_stage.add_system(hurt_enemies.before("death"));
update_stage.add_system(despawn_dead_enemies.label("death"));
// Setup test entities
let enemy_id = world.spawn().insert(Enemy { hit_points: 1 }).id();
// Run systems
update_stage.run(&mut world);
// Check resulting changes
assert!(world.get::<Enemy>(enemy_id).is_none());
}
#[test]
fn spawn_enemy_using_input_resource() {
// Setup world
let mut world = World::default();
// Setup stage with a system
let mut update_stage = SystemStage::parallel();
update_stage.add_system(spawn_enemy);
// Setup test resource
let mut input = Input::<KeyCode>::default();
input.press(KeyCode::Space);
world.insert_resource(input);
// Run systems
update_stage.run(&mut world);
// Check resulting changes, one entity has been spawned with `Enemy` component
assert_eq!(world.query::<&Enemy>().iter(&world).len(), 1);
// Clear the `just_pressed` status for all `KeyCode`s
world.resource_mut::<Input<KeyCode>>().clear();
// Run systems
update_stage.run(&mut world);
// Check resulting changes, no new entity has been spawned
assert_eq!(world.query::<&Enemy>().iter(&world).len(), 1);
}