add test for entity added internal event

src/events/internal-events.test.ts

@@ -0,0 +1,61 @@
+import {buildWorld} from "../ecs/ecs-world";
+import {Actions, createSystem, ReadEvents} from "../system/system";
+import {SimECSAddEntityEvent} from "./internal-events";
+import {Entity} from "../entity/entity";
+import {assert} from "chai";
+
+describe('Test internal events', () => {
+    it('Entity added', async () => {
+        // Count the number of times the add entity event was fired and read
+        let firedCount = 0;
+        // Count the amount of steps we already did
+        let loopCounter = 0;
+
+        // Will listen for added entity events
+        // and add to the firedCount
+        const EventListenerSystem = createSystem({
+            myEvents: ReadEvents(SimECSAddEntityEvent),
+        }).withRunFunction(({myEvents}) => {
+            myEvents.execute(() => {
+                firedCount++
+            });
+        }).build();
+
+        // Will add entities
+        const EventTriggerSystem = createSystem({
+            actions: Actions,
+        }).withRunFunction(async ({actions}) => {
+            actions.commands.addEntity(new Entity());
+        }).build();
+
+        // Will count the number of steps we took and end the simulation
+        const LoopCounterSystem = createSystem({
+            actions: Actions,
+        }).withRunFunction(({ actions }) => {
+            loopCounter++;
+            if (loopCounter >= 3) {
+                actions.commands.stopRun();
+            }
+        }).build();
+
+        const prepWorld = buildWorld()
+            .withDefaultScheduling(root => root
+                .addNewStage(stage => stage
+                    .addSystem(EventTriggerSystem)
+                    .addSystem(EventListenerSystem)
+                    .addSystem(LoopCounterSystem)
+                )
+            )
+            .build();
+
+        const runWorld = await prepWorld.prepareRun();
+
+        // Start and await the end of the simulation
+        await runWorld.start();
+
+        assert.equal(loopCounter, 3, 'Did not get to three steps exactly!');
+        // Since entities are added after the step, the first step will not fire an event,
+        // so the number of events will always be one smaller than the number of steps.
+        assert.equal(firedCount, loopCounter - 1, 'Not all added entities fired an event!');
+    });
+});