test: Add simple tests for scope.reconcile

src/state/ObservableScope.test.ts

@@ -5,9 +5,10 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { describe, expect, it } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { BehaviorSubject, combineLatest, Subject } from "rxjs";
 import { logger } from "matrix-js-sdk/lib/logger";
+import { sleep } from "matrix-js-sdk/lib/utils";
 
 import {
   Epoch,
@@ -102,3 +103,92 @@ describe("Epoch", () => {
     s$.complete();
   });
 });
+
+describe("Reconcile", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("should wait clean up before processing next", async () => {
+    vi.useFakeTimers();
+    const scope = new ObservableScope();
+    const behavior$ = new BehaviorSubject<number>(0);
+
+    const setup = vi.fn().mockImplementation(async () => await sleep(100));
+    const cleanup = vi
+      .fn()
+      .mockImplementation(async (n: number) => await sleep(100));
+    scope.reconcile(behavior$, async (value) => {
+      await setup();
+      return async (): Promise<void> => {
+        await cleanup(value);
+      };
+    });
+    // Let the initial setup process
+    await vi.advanceTimersByTimeAsync(120);
+    expect(setup).toHaveBeenCalledTimes(1);
+    expect(cleanup).toHaveBeenCalledTimes(0);
+
+    // Send next value
+    behavior$.next(1);
+    await vi.advanceTimersByTimeAsync(50);
+    // Should not have started setup for 1 yet
+    expect(setup).toHaveBeenCalledTimes(1);
+    expect(cleanup).toHaveBeenCalledTimes(1);
+    expect(cleanup).toHaveBeenCalledWith(0);
+
+    // Let cleanup finish
+    await vi.advanceTimersByTimeAsync(50);
+    // Now setup for 1 should have started
+    expect(setup).toHaveBeenCalledTimes(2);
+  });
+
+  it("should skip intermediates values that are not setup", async () => {
+    vi.useFakeTimers();
+    const scope = new ObservableScope();
+    const behavior$ = new BehaviorSubject<number>(0);
+
+    const setup = vi
+      .fn()
+      .mockImplementation(async (n: number) => await sleep(100));
+
+    const cleanupLock = Promise.withResolvers();
+    const cleanup = vi
+      .fn()
+      .mockImplementation(async (n: number) => await cleanupLock.promise);
+
+    scope.reconcile(behavior$, async (value) => {
+      await setup(value);
+      return async (): Promise<void> => {
+        await cleanup(value);
+      };
+    });
+    // Let the initial setup process (0)
+    await vi.advanceTimersByTimeAsync(120);
+
+    // Send 4 next values quickly
+    behavior$.next(1);
+    behavior$.next(2);
+    behavior$.next(3);
+    behavior$.next(4);
+
+    await vi.advanceTimersByTimeAsync(3000);
+    // should have only called cleanup for 0
+    expect(cleanup).toHaveBeenCalledTimes(1);
+    expect(cleanup).toHaveBeenCalledWith(0);
+    // Let cleanup finish
+    cleanupLock.resolve(undefined);
+    await vi.advanceTimersByTimeAsync(120);
+
+    // Now setup for 4 should have started, skipping 1,2,3
+    expect(setup).toHaveBeenCalledTimes(2);
+    expect(setup).toHaveBeenCalledWith(4);
+    expect(setup).not.toHaveBeenCalledWith(1);
+    expect(setup).not.toHaveBeenCalledWith(2);
+    expect(setup).not.toHaveBeenCalledWith(3);
+  });
+});