fix: ignore IPC messages not intended for Jest

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - `[jest-mock]` Treat cjs modules as objects so they can be mocked ([#13513](https://github.com/facebook/jest/pull/13513))
+- `[jest-worker]` Ignore IPC messages not intended for Jest ([#13543](https://github.com/facebook/jest/pull/13543))
 
 ### Chore & Maintenance
 

packages/jest-worker/src/workers/ChildProcessWorker.ts

@@ -255,6 +255,9 @@ export default class ChildProcessWorker
   }
 
   private _onMessage(response: ParentMessage) {
+    // Ignore messages not intended for us
+    if (!Array.isArray(response)) return;
+
     // TODO: Add appropriate type check
     let error: any;
 
@@ -311,7 +314,8 @@ export default class ChildProcessWorker
         break;
 
       default:
-        throw new TypeError(`Unexpected response from worker: ${response[0]}`);
+        // Ignore messages not intended for us
+        break;
     }
   }
 

packages/jest-worker/src/workers/__tests__/ChildProcessWorker.test.ts

@@ -363,7 +363,7 @@ it('creates error instances for known errors', () => {
   expect(callback3.mock.calls[0][0]).toBe(412);
 });
 
-it('throws when the child process returns a strange message', () => {
+it('does not throw when the child process returns a strange message', () => {
   const worker = new Worker({
     forkOptions: {},
     maxRetries: 3,
@@ -378,9 +378,14 @@ it('throws when the child process returns a strange message', () => {
   );
 
   // Type 27 does not exist.
-  expect(() => {
-    forkInterface.emit('message', [27]);
-  }).toThrow(TypeError);
+  forkInterface.emit('message', [27]);
+
+  forkInterface.emit('message', 'test');
+  forkInterface.emit('message', {foo: 'bar'});
+  forkInterface.emit('message', 0);
+  forkInterface.emit('message', null);
+  forkInterface.emit('message', Symbol('test'));
+  forkInterface.emit('message', true);
 });
 
 it('does not restart the child if it cleanly exited', () => {