example tests for systems

Author: mockersf

examples/README.md

@@ -47,6 +47,7 @@ git checkout v0.4.0
   - [Reflection](#reflection)
   - [Scene](#scene)
   - [Shaders](#shaders)
+  - [Tests](#tests)
   - [Tools](#tools)
   - [UI (User Interface)](#ui-user-interface)
   - [Window](#window)
@@ -195,6 +196,14 @@ Example | File | Description
 `shader_custom_material` | [`shader/shader_custom_material.rs`](./shader/shader_custom_material.rs) | Illustrates creating a custom material and a shader that uses it
 `shader_defs` | [`shader/shader_defs.rs`](./shader/shader_defs.rs) | Demonstrates creating a custom material that uses "shaders defs" (a tool to selectively toggle parts of a shader)
 
+## Tests
+
+Those are not in examples, but in the tests folder.
+
+Example | File | Description
+--- | --- | ---
+`how_to_test_systems` | [`../tests/how_to_test_systems.rs`](../tests/how_to_test_systems.rs) | How to tests systems with commands, queries or resources
+
 ## Tools
 
 Example | File | Description

tests/how_to_test_systems.rs

@@ -0,0 +1,119 @@
+use std::collections::HashMap;
+
+use bevy::{ecs::system::CommandQueue, prelude::*};
+
+struct Enemy {
+    hit_points: u32,
+}
+
+struct CharacterTemplate {
+    hit_points: HashMap<&'static str, u32>,
+}
+
+fn despawn_dead_enemies(mut commands: Commands, enemies: Query<(Entity, &Enemy)>) {
+    for (entity, enemy) in enemies.iter() {
+        if enemy.hit_points == 0 {
+            commands.despawn_recursive(entity);
+        }
+    }
+}
+
+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, character_template: Res<CharacterTemplate>) {
+    commands.spawn((Enemy {
+        hit_points: *character_template.hit_points.get("enemy").unwrap(),
+    },));
+}
+
+#[test]
+fn did_hurt_ennemy() {
+    // Setup world and commands
+    let mut world = World::default();
+    let mut queue = CommandQueue::default();
+    let mut commands = Commands::new(&mut queue, &world);
+
+    // Setup stage with our two systems
+    let mut update_stage = SystemStage::parallel();
+    update_stage.add_system(hurt_enemies.system().before("death"));
+    update_stage.add_system(despawn_dead_enemies.system().label("death"));
+    let mut schedule = Schedule::default();
+    schedule.add_stage("update", update_stage);
+
+    // Setup test entities
+    let ennemy_id = commands
+        .spawn((Enemy { hit_points: 5 },))
+        .current_entity()
+        .unwrap();
+    queue.apply(&mut world);
+
+    // Run systems
+    schedule.run(&mut world);
+
+    // Check resulting changes
+    assert!(world.get::<Enemy>(ennemy_id).is_some());
+    assert_eq!(world.get::<Enemy>(ennemy_id).unwrap().hit_points, 4);
+}
+
+#[test]
+fn did_despawn_ennemy() {
+    // Setup world and commands
+    let mut world = World::default();
+    let mut queue = CommandQueue::default();
+    let mut commands = Commands::new(&mut queue, &world);
+
+    // Setup stage with our two systems
+    let mut update_stage = SystemStage::parallel();
+    update_stage.add_system(hurt_enemies.system().before("death"));
+    update_stage.add_system(despawn_dead_enemies.system().label("death"));
+    let mut schedule = Schedule::default();
+    schedule.add_stage("update", update_stage);
+
+    // Setup test entities
+    let ennemy_id = commands
+        .spawn((Enemy { hit_points: 1 },))
+        .current_entity()
+        .unwrap();
+    queue.apply(&mut world);
+
+    // Run systems
+    schedule.run(&mut world);
+
+    // Check resulting changes
+    assert!(world.get::<Enemy>(ennemy_id).is_none());
+}
+
+#[test]
+fn spawned_from_resource() {
+    // Setup world and commands
+    let mut world = World::default();
+    let mut queue = CommandQueue::default();
+    let mut commands = Commands::new(&mut queue, &world);
+
+    // Setup stage with a system
+    let mut update_stage = SystemStage::parallel();
+    update_stage.add_system(spawn_enemy.system());
+    let mut schedule = Schedule::default();
+    schedule.add_stage("update", update_stage);
+
+    // Setup test resource
+    let mut hit_points = HashMap::new();
+    hit_points.insert("enemy", 25);
+    commands.insert_resource(CharacterTemplate { hit_points });
+    queue.apply(&mut world);
+
+    // Run systems
+    schedule.run(&mut world);
+
+    // Check resulting changes
+    let mut query = world.query::<&Enemy>();
+    let results = query
+        .iter(&world)
+        .map(|enemy| enemy.hit_points)
+        .collect::<Vec<_>>();
+    assert_eq!(results, vec![25]);
+}