diff --git a/desktop/app/src/dispatcher/__tests__/pluginManager.node.tsx b/desktop/app/src/dispatcher/__tests__/pluginManager.node.tsx
new file mode 100644
index 000000000..bed1e4a26
--- /dev/null
+++ b/desktop/app/src/dispatcher/__tests__/pluginManager.node.tsx
@@ -0,0 +1,108 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+jest.mock('../plugins');
+jest.mock('../../utils/electronModuleCache');
+import {loadPlugin} from '../../reducers/pluginManager';
+import {requirePlugin} from '../plugins';
+import {mocked} from 'ts-jest/utils';
+import {TestUtils} from 'flipper-plugin';
+import * as TestPlugin from '../../test-utils/TestPlugin';
+import {_SandyPluginDefinition as SandyPluginDefinition} from 'flipper-plugin';
+import MockFlipper from '../../test-utils/MockFlipper';
+
+const pluginDetails1 = TestUtils.createMockPluginDetails({
+  id: 'plugin1',
+  version: '0.0.1',
+});
+const pluginDefinition1 = new SandyPluginDefinition(pluginDetails1, TestPlugin);
+
+const pluginDetails1V2 = TestUtils.createMockPluginDetails({
+  id: 'plugin1',
+  version: '0.0.2',
+});
+const pluginDefinition1V2 = new SandyPluginDefinition(
+  pluginDetails1V2,
+  TestPlugin,
+);
+
+const pluginDetails2 = TestUtils.createMockPluginDetails({id: 'plugin2'});
+const pluginDefinition2 = new SandyPluginDefinition(pluginDetails2, TestPlugin);
+
+const mockedRequirePlugin = mocked(requirePlugin);
+
+let mockFlipper: MockFlipper;
+
+beforeEach(async () => {
+  mockedRequirePlugin.mockImplementation(
+    (details) =>
+      (details === pluginDetails1
+        ? pluginDefinition1
+        : details === pluginDetails2
+        ? pluginDefinition2
+        : details === pluginDetails1V2
+        ? pluginDefinition1V2
+        : undefined)!,
+  );
+  mockFlipper = new MockFlipper();
+  await mockFlipper.initWithDeviceAndClient({
+    clientOptions: {supportedPlugins: ['plugin1', 'plugin2']},
+  });
+});
+
+afterEach(async () => {
+  mockedRequirePlugin.mockReset();
+  await mockFlipper.destroy();
+});
+
+test('load plugin when no other version loaded', async () => {
+  mockFlipper.dispatch(
+    loadPlugin({plugin: pluginDetails1, enable: false, notifyIfFailed: false}),
+  );
+  expect(mockFlipper.getState().plugins.clientPlugins.get('plugin1')).toBe(
+    pluginDefinition1,
+  );
+  expect(mockFlipper.getState().plugins.loadedPlugins.get('plugin1')).toBe(
+    pluginDetails1,
+  );
+  expect(mockFlipper.clients[0].sandyPluginStates.has('plugin1')).toBeFalsy();
+});
+
+test('load plugin when other version loaded', async () => {
+  mockFlipper.dispatch(
+    loadPlugin({plugin: pluginDetails1, enable: false, notifyIfFailed: false}),
+  );
+  mockFlipper.dispatch(
+    loadPlugin({
+      plugin: pluginDetails1V2,
+      enable: false,
+      notifyIfFailed: false,
+    }),
+  );
+  expect(mockFlipper.getState().plugins.clientPlugins.get('plugin1')).toBe(
+    pluginDefinition1V2,
+  );
+  expect(mockFlipper.getState().plugins.loadedPlugins.get('plugin1')).toBe(
+    pluginDetails1V2,
+  );
+  expect(mockFlipper.clients[0].sandyPluginStates.has('plugin1')).toBeFalsy();
+});
+
+test('load and enable Sandy plugin', async () => {
+  mockFlipper.dispatch(
+    loadPlugin({plugin: pluginDetails1, enable: true, notifyIfFailed: false}),
+  );
+  expect(mockFlipper.getState().plugins.clientPlugins.get('plugin1')).toBe(
+    pluginDefinition1,
+  );
+  expect(mockFlipper.getState().plugins.loadedPlugins.get('plugin1')).toBe(
+    pluginDetails1,
+  );
+  expect(mockFlipper.clients[0].sandyPluginStates.has('plugin1')).toBeTruthy();
+});
diff --git a/desktop/app/src/dispatcher/pluginManager.tsx b/desktop/app/src/dispatcher/pluginManager.tsx
index e2c0144be..5b386a810 100644
--- a/desktop/app/src/dispatcher/pluginManager.tsx
+++ b/desktop/app/src/dispatcher/pluginManager.tsx
@@ -35,15 +35,29 @@ function refreshInstalledPlugins(store: Store) {
     .then((plugins) => store.dispatch(registerInstalledPlugins(plugins)));
 }
 
-export default (store: Store, _logger: Logger) => {
+export default (
+  store: Store,
+  _logger: Logger,
+  {runSideEffectsSynchronously}: {runSideEffectsSynchronously: boolean} = {
+    runSideEffectsSynchronously: false,
+  },
+) => {
   // This needn't happen immediately and is (light) I/O work.
-  window.requestIdleCallback(() => {
-    refreshInstalledPlugins(store);
-  });
+  if (window.requestIdleCallback) {
+    window.requestIdleCallback(() => {
+      refreshInstalledPlugins(store);
+    });
+  }
 
-  sideEffect(
+  const unsubscribeHandlePluginCommands = sideEffect(
     store,
-    {name: 'handlePluginActivation', throttleMs: 1000, fireImmediately: true},
+    {
+      name: 'handlePluginCommands',
+      throttleMs: 0,
+      fireImmediately: true,
+      runSynchronously: runSideEffectsSynchronously, // Used to simplify writing tests, if "true" passed, the all side effects will be called synchronously and immediately after changes
+      noTimeBudgetWarns: true, // These side effects are critical, so we're doing them with zero throttling and want to avoid unnecessary warns
+    },
     (state) => state.pluginManager.pluginCommandsQueue,
     (queue, store) => {
       for (const command of queue) {
@@ -59,6 +73,9 @@ export default (store: Store, _logger: Logger) => {
       store.dispatch(pluginCommandsProcessed(queue.length));
     },
   );
+  return async () => {
+    unsubscribeHandlePluginCommands();
+  };
 };
 
 function loadPlugin(store: Store, payload: LoadPluginActionPayload) {
diff --git a/desktop/app/src/reducers/__tests__/sandyplugins.node.tsx b/desktop/app/src/reducers/__tests__/sandyplugins.node.tsx
index 4c1620469..59fd4e7be 100644
--- a/desktop/app/src/reducers/__tests__/sandyplugins.node.tsx
+++ b/desktop/app/src/reducers/__tests__/sandyplugins.node.tsx
@@ -250,7 +250,9 @@ test('it can send messages from sandy clients', async () => {
 });
 
 test('it should initialize "Navigation" plugin if not enabled', async () => {
-  const {client, store} = await createMockFlipperWithPlugin(TestPlugin);
+  const {client, store} = await createMockFlipperWithPlugin(TestPlugin, {
+    supportedPlugins: ['Navigation'],
+  });
 
   const Plugin2 = new _SandyPluginDefinition(
     TestUtils.createMockPluginDetails({
diff --git a/desktop/app/src/test-utils/DeviceTestPlugin.tsx b/desktop/app/src/test-utils/DeviceTestPlugin.tsx
new file mode 100644
index 000000000..56ae32b5d
--- /dev/null
+++ b/desktop/app/src/test-utils/DeviceTestPlugin.tsx
@@ -0,0 +1,64 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import * as React from 'react';
+import {
+  DevicePluginClient,
+  Device,
+  usePlugin,
+  createState,
+  useValue,
+} from 'flipper-plugin';
+
+export function supportsDevice(_device: Device) {
+  return true;
+}
+
+export function devicePlugin(client: DevicePluginClient) {
+  const logStub = jest.fn();
+  const activateStub = jest.fn();
+  const deactivateStub = jest.fn();
+  const destroyStub = jest.fn();
+  const state = createState(
+    {
+      count: 0,
+    },
+    {
+      persist: 'counter',
+    },
+  );
+
+  client.device.onLogEntry((entry) => {
+    state.update((d) => {
+      d.count++;
+    });
+    logStub(entry);
+  });
+  client.onActivate(activateStub);
+  client.onDeactivate(deactivateStub);
+  client.onDestroy(destroyStub);
+
+  return {
+    logStub,
+    activateStub,
+    deactivateStub,
+    destroyStub,
+    state,
+  };
+}
+
+export function Component() {
+  const api = usePlugin(devicePlugin);
+  const count = useValue(api.state).count;
+
+  // @ts-expect-error
+  api.bla;
+
+  return <h1>Hi from test plugin {count}</h1>;
+}
diff --git a/desktop/app/src/test-utils/MockFlipper.tsx b/desktop/app/src/test-utils/MockFlipper.tsx
new file mode 100644
index 000000000..5bd91649e
--- /dev/null
+++ b/desktop/app/src/test-utils/MockFlipper.tsx
@@ -0,0 +1,213 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import {createStore} from 'redux';
+import BaseDevice from '../devices/BaseDevice';
+import {rootReducer} from '../store';
+import {Store} from '../reducers/index';
+import Client, {ClientQuery} from '../Client';
+import {buildClientId} from '../utils/clientUtils';
+import {Logger} from '../fb-interfaces/Logger';
+import {PluginDefinition} from '../plugin';
+import {registerPlugins} from '../reducers/plugins';
+import {getInstance} from '../fb-stubs/Logger';
+import {initializeFlipperLibImplementation} from '../utils/flipperLibImplementation';
+import pluginManager from '../dispatcher/pluginManager';
+
+export interface AppOptions {
+  plugins?: PluginDefinition[];
+}
+
+export interface ClientOptions {
+  name?: string;
+  supportedPlugins?: string[];
+  backgroundPlugins?: string[];
+  onSend?: (pluginId: string, method: string, params?: object) => any;
+  query?: ClientQuery;
+  skipRegister?: boolean;
+}
+
+export interface DeviceOptions {
+  serial?: string;
+}
+
+export default class MockFlipper {
+  private unsubscribePluginManager!: () => Promise<void>;
+  private _store!: Store;
+  private _logger!: Logger;
+  private _devices: BaseDevice[] = [];
+  private _clients: Client[] = [];
+  private _deviceCounter: number = 0;
+  private _clientCounter: number = 0;
+
+  public get store(): Store {
+    return this._store;
+  }
+
+  public get logger(): Logger {
+    return this._logger;
+  }
+
+  public get devices(): ReadonlyArray<BaseDevice> {
+    return this._devices;
+  }
+
+  public get clients(): ReadonlyArray<Client> {
+    return this._clients;
+  }
+
+  public get dispatch() {
+    return this._store.dispatch;
+  }
+
+  public getState() {
+    return this._store.getState();
+  }
+
+  public async init({plugins}: AppOptions = {}) {
+    this._store = createStore(rootReducer);
+    this._logger = getInstance();
+    this.unsubscribePluginManager = pluginManager(this._store, this._logger, {
+      runSideEffectsSynchronously: true,
+    });
+    initializeFlipperLibImplementation(this._store, this._logger);
+    this._store.dispatch(registerPlugins(plugins ?? []));
+  }
+
+  public async initWithDeviceAndClient(
+    {
+      appOptions = {},
+      deviceOptions = {},
+      clientOptions = {},
+    }: {
+      appOptions?: AppOptions;
+      deviceOptions?: DeviceOptions;
+      clientOptions?: ClientOptions;
+    } = {appOptions: {}, deviceOptions: {}, clientOptions: {}},
+  ): Promise<{flipper: MockFlipper; device: BaseDevice; client: Client}> {
+    await this.init(appOptions);
+    const device = this.createDevice(deviceOptions);
+    const client = await this.createClient(device, clientOptions);
+    return {
+      flipper: this,
+      device,
+      client,
+    };
+  }
+
+  public async destroy() {
+    this.unsubscribePluginManager && this.unsubscribePluginManager();
+  }
+
+  public createDevice({serial}: DeviceOptions = {}): BaseDevice {
+    const device = new BaseDevice(
+      serial ?? `serial_${++this._deviceCounter}`,
+      'physical',
+      'MockAndroidDevice',
+      'Android',
+    );
+    this._store.dispatch({
+      type: 'REGISTER_DEVICE',
+      payload: device,
+    });
+    device.loadDevicePlugins(this._store.getState().plugins.devicePlugins);
+    this._devices.push(device);
+    return device;
+  }
+
+  public async createClient(
+    device: BaseDevice,
+    {
+      name,
+      supportedPlugins,
+      backgroundPlugins,
+      onSend,
+      skipRegister,
+      query,
+    }: ClientOptions = {},
+  ): Promise<Client> {
+    if (!this._devices.includes(device)) {
+      throw new Error('The provided device does not exist');
+    }
+    query = query ?? {
+      app: name ?? `serial_${++this._clientCounter}`,
+      os: 'Android',
+      device: device.title,
+      device_id: device.serial,
+      sdk_version: 4,
+    };
+    const id = buildClientId({
+      app: query.app,
+      os: query.os,
+      device: query.device,
+      device_id: query.device_id,
+    });
+    supportedPlugins =
+      supportedPlugins ??
+      [...this._store.getState().plugins.clientPlugins.values()].map(
+        (p) => p.id,
+      );
+    const client = new Client(
+      id,
+      query,
+      null, // create a stub connection to avoid this plugin to be archived?
+      this._logger,
+      this._store,
+      supportedPlugins,
+      device,
+    );
+
+    // yikes
+    client.device = {
+      then() {
+        return device;
+      },
+    } as any;
+    client.rawCall = async (
+      method: string,
+      _fromPlugin: boolean,
+      params: any,
+    ): Promise<any> => {
+      const intercepted = onSend?.(method, params);
+      if (intercepted !== undefined) {
+        return intercepted;
+      }
+      switch (method) {
+        case 'getPlugins':
+          // assuming this plugin supports all plugins for now
+          return {
+            plugins: supportedPlugins,
+          };
+        case 'getBackgroundPlugins':
+          return {
+            plugins: backgroundPlugins ?? [],
+          };
+        default:
+          throw new Error(
+            `Test client doesn't support rawCall method '${method}'`,
+          );
+      }
+    };
+    client.rawSend = jest.fn();
+
+    await client.init();
+
+    // As convenience, by default we select the new client, star the plugin, and select it
+    if (!skipRegister) {
+      this._store.dispatch({
+        type: 'NEW_CLIENT',
+        payload: client,
+      });
+    }
+
+    this._clients.push(client);
+
+    return client;
+  }
+}
diff --git a/desktop/app/src/test-utils/TestPlugin.tsx b/desktop/app/src/test-utils/TestPlugin.tsx
new file mode 100644
index 000000000..ba7686802
--- /dev/null
+++ b/desktop/app/src/test-utils/TestPlugin.tsx
@@ -0,0 +1,98 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import * as React from 'react';
+import {PluginClient, usePlugin, createState, useValue} from 'flipper-plugin';
+
+type Events = {
+  inc: {
+    delta: number;
+  };
+};
+
+type Methods = {
+  currentState(params: {since: number}): Promise<number>;
+};
+
+export function plugin(client: PluginClient<Events, Methods>) {
+  const connectStub = jest.fn();
+  const disconnectStub = jest.fn();
+  const activateStub = jest.fn();
+  const deactivateStub = jest.fn();
+  const destroyStub = jest.fn();
+  const state = createState(
+    {
+      count: 0,
+    },
+    {
+      persist: 'counter',
+    },
+  );
+  const unhandledMessages = createState<any[]>([]);
+
+  client.onConnect(connectStub);
+  client.onDisconnect(disconnectStub);
+  client.onActivate(activateStub);
+  client.onDeactivate(deactivateStub);
+  client.onDestroy(destroyStub);
+  client.onMessage('inc', ({delta}) => {
+    state.update((draft) => {
+      draft.count += delta;
+    });
+  });
+  client.onUnhandledMessage((event, params) => {
+    unhandledMessages.update((draft) => {
+      draft.push({event, params});
+    });
+  });
+
+  function _unused_JustTypeChecks() {
+    // @ts-expect-error Argument of type '"bla"' is not assignable
+    client.send('bla', {});
+    // @ts-expect-error Argument of type '{ stuff: string; }' is not assignable to parameter of type
+    client.send('currentState', {stuff: 'nope'});
+    // @ts-expect-error
+    client.onMessage('stuff', (_params) => {
+      // noop
+    });
+    client.onMessage('inc', (params) => {
+      // @ts-expect-error
+      params.bla;
+    });
+  }
+
+  async function getCurrentState() {
+    return client.send('currentState', {since: 0});
+  }
+
+  expect(client.device).not.toBeNull();
+
+  return {
+    activateStub,
+    deactivateStub,
+    connectStub,
+    destroyStub,
+    disconnectStub,
+    getCurrentState,
+    state,
+    unhandledMessages,
+    appId: client.appId,
+    appName: client.appName,
+  };
+}
+
+export function Component() {
+  const api = usePlugin(plugin);
+  const count = useValue(api.state).count;
+
+  // @ts-expect-error
+  api.bla;
+
+  return <h1>Hi from test plugin {count}</h1>;
+}
diff --git a/desktop/app/src/test-utils/createMockFlipperWithPlugin.tsx b/desktop/app/src/test-utils/createMockFlipperWithPlugin.tsx
index 00591a7e0..11dfdfd01 100644
--- a/desktop/app/src/test-utils/createMockFlipperWithPlugin.tsx
+++ b/desktop/app/src/test-utils/createMockFlipperWithPlugin.tsx
@@ -8,7 +8,6 @@
  */
 
 import React from 'react';
-import {createStore} from 'redux';
 import {Provider} from 'react-redux';
 import {
   render,
@@ -25,18 +24,14 @@ import {
 } from '../reducers/connections';
 import BaseDevice from '../devices/BaseDevice';
 
-import {rootReducer} from '../store';
 import {Store} from '../reducers/index';
 import Client, {ClientQuery} from '../Client';
 
-import {buildClientId} from '../utils/clientUtils';
 import {Logger} from '../fb-interfaces/Logger';
 import {PluginDefinition} from '../plugin';
-import {registerPlugins} from '../reducers/plugins';
 import PluginContainer from '../PluginContainer';
 import {getPluginKey, isDevicePluginDefinition} from '../utils/pluginUtils';
-import {getInstance} from '../fb-stubs/Logger';
-import {initializeFlipperLibImplementation} from '../utils/flipperLibImplementation';
+import MockFlipper from './MockFlipper';
 
 export type MockFlipperResult = {
   client: Client;
@@ -64,94 +59,35 @@ type MockOptions = Partial<{
   additionalPlugins?: PluginDefinition[];
   dontEnableAdditionalPlugins?: true;
   asBackgroundPlugin?: true;
+  supportedPlugins?: string[];
 }>;
 
 export async function createMockFlipperWithPlugin(
   pluginClazz: PluginDefinition,
   options?: MockOptions,
 ): Promise<MockFlipperResult> {
-  const store = createStore(rootReducer);
-  const logger = getInstance();
-  initializeFlipperLibImplementation(store, logger);
-  store.dispatch(
-    registerPlugins([pluginClazz, ...(options?.additionalPlugins ?? [])]),
-  );
+  const mockFlipper = new MockFlipper();
+  await mockFlipper.init({
+    plugins: [pluginClazz, ...(options?.additionalPlugins ?? [])],
+  });
+  const logger = mockFlipper.logger;
+  const store = mockFlipper.store;
 
-  function createDevice(serial: string): BaseDevice {
-    const device = new BaseDevice(
-      serial,
-      'physical',
-      'MockAndroidDevice',
-      'Android',
-    );
-    store.dispatch({
-      type: 'REGISTER_DEVICE',
-      payload: device,
-    });
-    device.loadDevicePlugins(store.getState().plugins.devicePlugins);
-    return device;
-  }
-
-  async function createClient(
+  const createDevice = (serial: string) => mockFlipper.createDevice({serial});
+  const createClient = async (
     device: BaseDevice,
     name: string,
     query?: ClientQuery,
     skipRegister?: boolean,
-  ): Promise<Client> {
-    query = query ?? {
-      app: name,
-      os: 'Android',
-      device: device.title,
-      device_id: device.serial,
-      sdk_version: 4,
-    };
-    const id = buildClientId({
-      app: query.app,
-      os: query.os,
-      device: query.device,
-      device_id: query.device_id,
-    });
-
-    const client = new Client(
-      id,
+  ) => {
+    const client = await mockFlipper.createClient(device, {
+      name,
       query,
-      null, // create a stub connection to avoid this plugin to be archived?
-      logger,
-      store,
-      [
-        ...(isDevicePluginDefinition(pluginClazz) ? [] : [pluginClazz.id]),
-        ...(options?.dontEnableAdditionalPlugins
-          ? []
-          : options?.additionalPlugins?.map((p) => p.id) ?? []),
-      ],
-      device,
-    );
-
-    client.rawCall = async (
-      method: string,
-      _fromPlugin: boolean,
-      params: any,
-    ): Promise<any> => {
-      const intercepted = options?.onSend?.(method, params);
-      if (intercepted !== undefined) {
-        return intercepted;
-      }
-      switch (method) {
-        case 'getPlugins':
-          // assuming this plugin supports all plugins for now
-          return {
-            plugins: [...store.getState().plugins.clientPlugins.keys()],
-          };
-        case 'getBackgroundPlugins':
-          return {plugins: options?.asBackgroundPlugin ? [pluginClazz.id] : []};
-        default:
-          throw new Error(
-            `Test client doesn't support rawCall method '${method}'`,
-          );
-      }
-    };
-    client.rawSend = jest.fn();
-
+      skipRegister,
+      onSend: options?.onSend,
+      supportedPlugins: options?.supportedPlugins,
+      backgroundPlugins: options?.asBackgroundPlugin ? [pluginClazz.id] : [],
+    });
     // enable the plugin
     if (
       !isDevicePluginDefinition(pluginClazz) &&
@@ -180,17 +116,8 @@ export async function createMockFlipperWithPlugin(
         }
       });
     }
-    await client.init();
-
-    // As convenience, by default we select the new client, star the plugin, and select it
-    if (!skipRegister) {
-      store.dispatch({
-        type: 'NEW_CLIENT',
-        payload: client,
-      });
-    }
     return client;
-  }
+  };
 
   const device = createDevice('serial');
   const client = await createClient(device, 'TestApp');
diff --git a/desktop/app/src/utils/sideEffect.tsx b/desktop/app/src/utils/sideEffect.tsx
index b9097be5b..46d0f9821 100644
--- a/desktop/app/src/utils/sideEffect.tsx
+++ b/desktop/app/src/utils/sideEffect.tsx
@@ -28,7 +28,13 @@ export function sideEffect<
   State = Store extends ReduxStore<infer S, any> ? S : never
 >(
   store: Store,
-  options: {name: string; throttleMs: number; fireImmediately?: boolean},
+  options: {
+    name: string;
+    throttleMs: number;
+    fireImmediately?: boolean;
+    noTimeBudgetWarns?: boolean;
+    runSynchronously?: boolean;
+  },
   selector: (state: State) => V,
   effect: (selectedState: V, store: Store) => void,
 ): () => void {
@@ -52,7 +58,11 @@ export function sideEffect<
     }
     lastRun = performance.now();
     const duration = lastRun - start;
-    if (duration > 15 && duration > options.throttleMs / 10) {
+    if (
+      !options.noTimeBudgetWarns &&
+      duration > 15 &&
+      duration > options.throttleMs / 10
+    ) {
       console.warn(
         `Side effect '${options.name}' took ${Math.round(
           duration,
@@ -75,13 +85,17 @@ export function sideEffect<
       return; // no new value, no need to schedule
     }
     scheduled = true;
-    timeout = setTimeout(
-      run,
-      // Run ASAP (but async) or, if we recently did run, delay until at least 'throttle' time has expired
-      lastRun === -1
-        ? 1
-        : Math.max(1, lastRun + options.throttleMs - performance.now()),
-    );
+    if (options.runSynchronously) {
+      run();
+    } else {
+      timeout = setTimeout(
+        run,
+        // Run ASAP (but async) or, if we recently did run, delay until at least 'throttle' time has expired
+        lastRun === -1
+          ? 1
+          : Math.max(1, lastRun + options.throttleMs - performance.now()),
+      );
+    }
   });
 
   if (options.fireImmediately) {