fix(core-backend): control randomness to fix flaky test

Author: Kriys94

packages/core-backend/src/BackendWebSocketService.test.ts

@@ -817,6 +817,9 @@ describe('BackendWebSocketService', () => {
     it('should skip connect when reconnect timer is already scheduled', async () => {
       await withService(
         async ({ service, getMockWebSocket, completeAsyncOperations }) => {
+          // Mock Math.random to make Cockatiel's jitter deterministic
+          jest.spyOn(Math, 'random').mockReturnValue(0);
+
           // Connect successfully first
           await service.connect();
 
@@ -952,6 +955,9 @@ describe('BackendWebSocketService', () => {
     it('should not schedule multiple reconnects when scheduleReconnect called multiple times', async () => {
       await withService(
         async ({ service, getMockWebSocket, completeAsyncOperations }) => {
+          // Mock Math.random to make Cockatiel's jitter deterministic
+          jest.spyOn(Math, 'random').mockReturnValue(0);
+
           await service.connect();
           expect(service.getConnectionInfo().state).toBe(
             WebSocketState.CONNECTED,
@@ -987,6 +993,9 @@ describe('BackendWebSocketService', () => {
     it('should force reconnection and schedule connect', async () => {
       await withService(
         async ({ service, getMockWebSocket, completeAsyncOperations }) => {
+          // Mock Math.random to make Cockatiel's jitter deterministic
+          jest.spyOn(Math, 'random').mockReturnValue(0);
+
           await service.connect();
           expect(service.getConnectionInfo().state).toBe(
             WebSocketState.CONNECTED,
@@ -1018,6 +1027,9 @@ describe('BackendWebSocketService', () => {
       await withService(
         { mockWebSocketOptions: { autoConnect: false } },
         async ({ service, getMockWebSocket, completeAsyncOperations }) => {
+          // Mock Math.random to make Cockatiel's jitter deterministic
+          jest.spyOn(Math, 'random').mockReturnValue(0);
+
           // Trigger a connection failure to schedule a reconnect
           // eslint-disable-next-line @typescript-eslint/no-floating-promises
           service.connect();