write tests for AsyncMappedList

src/mocks/ListObserver.js

@@ -16,67 +16,46 @@ limitations under the License.
 
 export class ListObserver {
     constructor() {
-        this._queuesPerType = new Map();
+        this._queue = [];
+        this._backlog = [];
     }
 
-    _nextEvent(type) {
-        let queue = this._queuesPerType.get(type);
-        if (!queue) {
-            queue = [];
-            this._queuesPerType.set(type, queue);
+    next() {
+        if (this._backlog.length) {
+            return Promise.resolve(this._backlog.shift());
+        } else {
+            return new Promise(resolve => {
+                this._queue.push(resolve);
+            });
         }
-        return new Promise(resolve => {
-            queue.push(resolve);
-        });
     }
 
-    nextAdd() {
-        return this._nextEvent("add");
-    }
-
-    nextUpdate() {
-        return this._nextEvent("update");
-    }
-
-    nextRemove() {
-        return this._nextEvent("remove");
-    }
-
-    nextMove() {
-        return this._nextEvent("move");
-    }
-
-    nextReset() {
-        return this._nextEvent("reset");
-    }
-
-    _popQueue(type) {
-        const queue = this._queuesPerType.get(type);
-        return queue?.unshift();
+    _fullfillNext(value) {
+        if (this._queue.length) {
+            const resolve = this._queue.shift();
+            resolve(value);
+        } else {
+            this._backlog.push(value);
+        }
     }
 
     onReset() {
-        const resolve = this._popQueue("reset");
-        resolve && resolve();
+        this._fullfillNext({type: "reset"});
     }
     
     onAdd(index, value) {
-        const resolve = this._popQueue("add");
-        resolve && resolve({index, value});
+        this._fullfillNext({type: "add", index, value});
     }
     
     onUpdate(index, value, params) {
-        const resolve = this._popQueue("update");
-        resolve && resolve({index, value, params});
+        this._fullfillNext({type: "update", index, value, params});
     }
     
     onRemove(index, value) {
-        const resolve = this._popQueue("remove");
-        resolve && resolve({index, value});
+        this._fullfillNext({type: "remove", index, value});
     }
 
     onMove(fromIdx, toIdx, value) {
-        const resolve = this._popQueue("move");
-        resolve && resolve({fromIdx, toIdx, value});
+        this._fullfillNext({type: "move", fromIdx, toIdx, value});
     }
 }

src/observable/list/AsyncMappedList.js

@@ -143,8 +143,55 @@ class ResetEvent {
     }
 }
 
+import {ObservableArray} from "./ObservableArray.js";
+import {ListObserver} from "../../mocks/ListObserver.js";
+
 export function tests() {
     return {
-
+        "events are emitted in order": async assert => {
+            const double = n => n * n;
+            const source = new ObservableArray();
+            const mapper = new AsyncMappedList(source, async n => {
+                await new Promise(r => setTimeout(r, n));
+                return {n: double(n)};
+            }, (o, params, n) => {
+                o.n = double(n);
+            });
+            const observer = new ListObserver();
+            mapper.subscribe(observer);
+            source.append(2); // will sleep this amount, so second append would take less time
+            source.append(1);
+            source.update(0, 7, "lucky seven")
+            source.remove(0);
+            {
+                const {type, index, value} = await observer.next();
+                assert.equal(mapper.length, 1);
+                assert.equal(type, "add");
+                assert.equal(index, 0);
+                assert.equal(value.n, 4);
+            }
+            {
+                const {type, index, value} = await observer.next();
+                assert.equal(mapper.length, 2);
+                assert.equal(type, "add");
+                assert.equal(index, 1);
+                assert.equal(value.n, 1);
+            }
+            {
+                const {type, index, value, params} = await observer.next();
+                assert.equal(mapper.length, 2);
+                assert.equal(type, "update");
+                assert.equal(index, 0);
+                assert.equal(value.n, 49);
+                assert.equal(params, "lucky seven");
+            }
+            {
+                const {type, index, value} = await observer.next();
+                assert.equal(mapper.length, 1);
+                assert.equal(type, "remove");
+                assert.equal(index, 0);
+                assert.equal(value.n, 49);
+            }
+        }
     }
 }

src/observable/list/ObservableArray.js

@@ -44,6 +44,13 @@ export class ObservableArray extends BaseObservableList {
         this.emitAdd(idx, item);
     }
 
+    update(idx, item, params = null) {
+        if (idx < this._items.length) {
+            this._items[idx] = item;
+            this.emitUpdate(idx, item, params);
+        }
+    }
+
     get array() {
         return this._items;
     }