Command processing (2/n): testing

Summary:
*Stack summary*: this stack refactors plugin management actions to perform them in a dispatcher rather than in the root reducer (store.tsx) as all of these actions has side effects. To do that, we store requested plugin management actions (install/update/uninstall, star/unstar) in a queue which is then handled by pluginManager dispatcher. This dispatcher then dispatches all required state updates.

*Diff summary*: refactored Flipper mocking helpers to allow testing of plugin commands, and wrote some tests for pluginManager.

Reviewed By: mweststrate

Differential Revision: D26450344

fbshipit-source-id: 0e8414517cc1ad353781dffd7ffb4a5f9a815d38

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>;
+}