diff --git a/libraries/browser-tracker-core/test/out_queue.test.ts b/libraries/browser-tracker-core/test/out_queue.test.ts
index b5e8668f9..e3088b06c 100644
--- a/libraries/browser-tracker-core/test/out_queue.test.ts
+++ b/libraries/browser-tracker-core/test/out_queue.test.ts
@@ -40,21 +40,20 @@ const readPostQueue = () => {
 describe('OutQueueManager', () => {
   const maxQueueSize = 2;
 
-  var xhrMock: XMLHttpRequest;
+  var xhrMock: Partial<XMLHttpRequest>;
   var xhrOpenMock: jest.Mock;
   beforeEach(() => {
     localStorage.clear();
 
     xhrOpenMock = jest.fn();
     xhrMock = {
-      ...new XMLHttpRequest(),
       open: xhrOpenMock,
       send: jest.fn(),
       setRequestHeader: jest.fn(),
       withCredentials: true,
     };
 
-    jest.spyOn(window, 'XMLHttpRequest').mockImplementation(() => xhrMock);
+    jest.spyOn(window, 'XMLHttpRequest').mockImplementation(() => xhrMock as XMLHttpRequest);
   });
 
   const respondMockRequest = (status: number) => {
@@ -371,7 +370,7 @@ describe('OutQueueManager', () => {
       let retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
 
-      xhrMock.onabort?.(new ProgressEvent('abort'));
+      (xhrMock as XMLHttpRequest).ontimeout?.(new ProgressEvent('abort'));
 
       retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
@@ -384,7 +383,7 @@ describe('OutQueueManager', () => {
       let retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
 
-      xhrMock.ontimeout?.(new ProgressEvent('timeout'));
+      (xhrMock as XMLHttpRequest).ontimeout?.(new ProgressEvent('timeout'));
 
       retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
@@ -397,7 +396,7 @@ describe('OutQueueManager', () => {
       let retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
 
-      xhrMock.onerror?.(new ProgressEvent('error'));
+      (xhrMock as XMLHttpRequest).onerror?.(new ProgressEvent('error'));
 
       retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
@@ -435,7 +434,7 @@ describe('OutQueueManager', () => {
       let retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
 
-      xhrMock.onabort?.(new ProgressEvent('abort'));
+      (xhrMock as XMLHttpRequest).ontimeout?.(new ProgressEvent('abort'));
 
       retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(0);
@@ -448,7 +447,7 @@ describe('OutQueueManager', () => {
       let retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
 
-      xhrMock.ontimeout?.(new ProgressEvent('timeout'));
+      (xhrMock as XMLHttpRequest).ontimeout?.(new ProgressEvent('timeout'));
 
       retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(0);
@@ -461,7 +460,7 @@ describe('OutQueueManager', () => {
       let retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(1);
 
-      xhrMock.onerror?.(new ProgressEvent('error'));
+      (xhrMock as XMLHttpRequest).onerror?.(new ProgressEvent('error'));
 
       retrievedQueue = readPostQueue();
       expect(retrievedQueue).toHaveLength(0);