diff --git a/desktop/flipper-server-core/src/plugins/ServerAddOn.tsx b/desktop/flipper-server-core/src/plugins/ServerAddOn.tsx
index 37e207dda..bb03c8f30 100644
--- a/desktop/flipper-server-core/src/plugins/ServerAddOn.tsx
+++ b/desktop/flipper-server-core/src/plugins/ServerAddOn.tsx
@@ -12,42 +12,11 @@ import {assertNotNull} from '../comms/Utilities';
 import {
   FlipperServerForServerAddOn,
   ServerAddOnCleanup,
-  ServerAddOn as ServerAddOnFn,
   ServerAddOnStartDetails,
 } from 'flipper-common';
 import {ServerAddOnDesktopToModuleConnection} from './ServerAddOnDesktopToModuleConnection';
 import {ServerAddOnModuleToDesktopConnection} from './ServerAddOnModuleToDesktopConnection';
-// @ts-ignore
-import defaultPlugins from '../defaultPlugins';
-
-interface ServerAddOnModule {
-  default: ServerAddOnFn;
-}
-
-const loadPlugin = (
-  pluginName: string,
-  details: ServerAddOnStartDetails,
-): ServerAddOnModule => {
-  console.debug('loadPlugin', pluginName, details);
-
-  if (details.isBundled) {
-    const bundledPlugin = defaultPlugins[pluginName];
-    assertNotNull(
-      bundledPlugin,
-      `loadPlugin (isBundled = true) -> plugin ${pluginName} not found.`,
-    );
-    return bundledPlugin;
-  }
-
-  assertNotNull(
-    details.path,
-    `loadPlugin (isBundled = false) -> server add-on path is empty plugin ${pluginName}.`,
-  );
-
-  // eslint-disable-next-line no-eval
-  const serverAddOnModule = eval(`require("${details.path}")`);
-  return serverAddOnModule;
-};
+import {loadServerAddOn} from './loadServerAddOn';
 
 export class ServerAddOn {
   private owners: Set<string>;
@@ -69,7 +38,7 @@ export class ServerAddOn {
   ): Promise<ServerAddOn> {
     console.info('ServerAddOn.start', pluginName, details);
 
-    const {default: serverAddOn} = loadPlugin(pluginName, details);
+    const {default: serverAddOn} = loadServerAddOn(pluginName, details);
     assertNotNull(serverAddOn);
     assert(
       typeof serverAddOn === 'function',
diff --git a/desktop/flipper-server-core/src/plugins/__tests__/ServerAddOn.node.tsx b/desktop/flipper-server-core/src/plugins/__tests__/ServerAddOn.node.tsx
new file mode 100644
index 000000000..05e8744f7
--- /dev/null
+++ b/desktop/flipper-server-core/src/plugins/__tests__/ServerAddOn.node.tsx
@@ -0,0 +1,157 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and 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 {ServerAddOnStartDetails} from 'flipper-common';
+import {loadServerAddOn} from '../loadServerAddOn';
+import {ServerAddOn} from '../ServerAddOn';
+import {ServerAddOnModuleToDesktopConnection} from '../ServerAddOnModuleToDesktopConnection';
+
+jest.mock('../loadServerAddOn');
+const loadServerAddOnMock = loadServerAddOn as jest.Mock;
+
+const createControlledPromise = () => {
+  let resolve!: () => void;
+  let reject!: (reason: unknown) => void;
+  const promise = new Promise<void>((resolveP, rejectP) => {
+    resolve = resolveP;
+    reject = rejectP;
+  });
+  return {
+    promise,
+    resolve,
+    reject,
+  };
+};
+
+describe('ServerAddOn', () => {
+  const pluginName = 'lightSaber';
+  const initialOwner = 'yoda';
+  const detailsBundled: ServerAddOnStartDetails = {
+    isBundled: true,
+  };
+  const detailsInstalled: ServerAddOnStartDetails = {
+    path: '/dagobar/',
+  };
+
+  const startServerAddOn = async (details: ServerAddOnStartDetails) => {
+    const addOnCleanupMock = jest.fn();
+    const addOnMock = jest.fn().mockImplementation(() => addOnCleanupMock);
+    loadServerAddOnMock.mockImplementation(() => ({
+      default: addOnMock,
+    }));
+
+    const flipperServer = {
+      connect: jest.fn(),
+      on: jest.fn(),
+      off: jest.fn(),
+      exec: jest.fn(),
+      close: jest.fn(),
+      emit: jest.fn(),
+    };
+
+    expect(loadServerAddOnMock).toBeCalledTimes(0);
+    expect(addOnMock).toBeCalledTimes(0);
+    expect(addOnCleanupMock).toBeCalledTimes(0);
+
+    const serverAddOn = await ServerAddOn.start(
+      pluginName,
+      details,
+      initialOwner,
+      flipperServer,
+    );
+
+    expect(loadServerAddOnMock).toBeCalledTimes(1);
+    expect(loadServerAddOnMock).toBeCalledWith(pluginName, details);
+    expect(addOnMock).toBeCalledTimes(1);
+    expect(addOnMock).toBeCalledWith(
+      expect.any(ServerAddOnModuleToDesktopConnection),
+      {
+        flipperServer,
+      },
+    );
+
+    return {
+      addOnCleanupMock,
+      addOnMock,
+      flipperServer,
+      serverAddOn,
+    };
+  };
+
+  describe.each([
+    ['bundled', detailsBundled],
+    ['installed', detailsInstalled],
+  ])('%s', (_name, details) => {
+    test('stops the add-on when the initial owner is removed', async () => {
+      const {serverAddOn, addOnCleanupMock} = await startServerAddOn(details);
+
+      const controlledP = createControlledPromise();
+      addOnCleanupMock.mockImplementation(() => controlledP.promise);
+
+      const removeOwnerRes = serverAddOn.removeOwner(initialOwner);
+
+      expect(removeOwnerRes).toBeInstanceOf(Promise);
+      expect(addOnCleanupMock).toBeCalledTimes(1);
+
+      controlledP.resolve();
+      await removeOwnerRes;
+    });
+
+    test('adds a new owner, stops the add-on when all owners are removed', async () => {
+      const {serverAddOn, addOnCleanupMock} = await startServerAddOn(details);
+
+      const newOwner = 'luke';
+      serverAddOn.addOwner(newOwner);
+
+      const controlledP = createControlledPromise();
+      addOnCleanupMock.mockImplementation(() => controlledP.promise);
+
+      const removeOwnerRes1 = serverAddOn.removeOwner(initialOwner);
+      expect(removeOwnerRes1).toBeUndefined();
+      expect(addOnCleanupMock).toBeCalledTimes(0);
+
+      const removeOwnerRes2 = serverAddOn.removeOwner(newOwner);
+
+      expect(removeOwnerRes2).toBeInstanceOf(Promise);
+      expect(addOnCleanupMock).toBeCalledTimes(1);
+
+      controlledP.resolve();
+      await removeOwnerRes2;
+    });
+
+    test('does nothing when removeOwner is called with a missing owner', async () => {
+      const {serverAddOn, addOnCleanupMock} = await startServerAddOn(details);
+
+      const missingOwner = 'luke';
+
+      const removeOwnerRes = serverAddOn.removeOwner(missingOwner);
+      expect(addOnCleanupMock).toBeCalledTimes(0);
+      expect(removeOwnerRes).toBeUndefined();
+    });
+
+    test('calls stop only once when removeOwner is called twice with the same owner', async () => {
+      const {serverAddOn, addOnCleanupMock} = await startServerAddOn(details);
+
+      const controlledP = createControlledPromise();
+      addOnCleanupMock.mockImplementation(() => controlledP.promise);
+
+      const removeOwnerRes1 = serverAddOn.removeOwner(initialOwner);
+
+      expect(removeOwnerRes1).toBeInstanceOf(Promise);
+      expect(addOnCleanupMock).toBeCalledTimes(1);
+
+      const removeOwnerRes2 = serverAddOn.removeOwner(initialOwner);
+      expect(removeOwnerRes2).toBeUndefined();
+      expect(addOnCleanupMock).toBeCalledTimes(1);
+
+      controlledP.resolve();
+      await removeOwnerRes1;
+    });
+  });
+});
diff --git a/desktop/flipper-server-core/src/plugins/loadServerAddOn.tsx b/desktop/flipper-server-core/src/plugins/loadServerAddOn.tsx
new file mode 100644
index 000000000..62f27f35e
--- /dev/null
+++ b/desktop/flipper-server-core/src/plugins/loadServerAddOn.tsx
@@ -0,0 +1,46 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and 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 {
+  ServerAddOn as ServerAddOnFn,
+  ServerAddOnStartDetails,
+} from 'flipper-common';
+import {assertNotNull} from '../comms/Utilities';
+// The file is generated automatically by "prepareDefaultPlugins" in "scripts"
+// @ts-ignore
+import defaultPlugins from '../defaultPlugins';
+
+interface ServerAddOnModule {
+  default: ServerAddOnFn;
+}
+
+export const loadServerAddOn = (
+  pluginName: string,
+  details: ServerAddOnStartDetails,
+): ServerAddOnModule => {
+  console.debug('loadPlugin', pluginName, details);
+
+  if (details.isBundled) {
+    const bundledPlugin = defaultPlugins[pluginName];
+    assertNotNull(
+      bundledPlugin,
+      `loadPlugin (isBundled = true) -> plugin ${pluginName} not found.`,
+    );
+    return bundledPlugin;
+  }
+
+  assertNotNull(
+    details.path,
+    `loadPlugin (isBundled = false) -> server add-on path is empty plugin ${pluginName}.`,
+  );
+
+  // eslint-disable-next-line no-eval
+  const serverAddOnModule = eval(`require("${details.path}")`);
+  return serverAddOnModule;
+};