diff --git a/packages/core/src/tools/instrumentMethod.spec.ts b/packages/core/src/tools/instrumentMethod.spec.ts
index c2f2988a55..dffe604a1d 100644
--- a/packages/core/src/tools/instrumentMethod.spec.ts
+++ b/packages/core/src/tools/instrumentMethod.spec.ts
@@ -204,11 +204,10 @@ describe('instrumentSetter', () => {
 
   beforeEach(() => {
     clock = mockClock()
-    zoneJs = mockZoneJs()
-
     registerCleanupTask(() => {
       clock.cleanup()
     })
+    zoneJs = mockZoneJs()
   })
 
   it('replaces the original setter', () => {
diff --git a/packages/core/src/tools/timer.spec.ts b/packages/core/src/tools/timer.spec.ts
index f1c4bff7df..4bbc21fa57 100644
--- a/packages/core/src/tools/timer.spec.ts
+++ b/packages/core/src/tools/timer.spec.ts
@@ -21,11 +21,11 @@ import { noop } from './utils/functionUtils'
 
     beforeEach(() => {
       clock = mockClock()
-      zoneJs = mockZoneJs()
       registerCleanupTask(() => {
         clock.cleanup()
         resetMonitor()
       })
+      zoneJs = mockZoneJs()
     })
 
     it('executes the callback asynchronously', () => {
diff --git a/packages/core/test/leakDetection.ts b/packages/core/test/leakDetection.ts
index 523e73a5a0..01d7f001a8 100644
--- a/packages/core/test/leakDetection.ts
+++ b/packages/core/test/leakDetection.ts
@@ -1,23 +1,21 @@
 import { display } from '../src/tools/display'
 import { isIE } from '../src/tools/utils/browserDetection'
 import { getCurrentJasmineSpec } from './getCurrentJasmineSpec'
-
-let originalAddEventListener: typeof EventTarget.prototype.addEventListener
-let originalRemoveEventListener: typeof EventTarget.prototype.removeEventListener
-let wrappedListeners: {
-  [key: string]: Map<EventListenerOrEventListenerObject | null, EventListenerOrEventListenerObject | null>
-}
+import { registerCleanupTask } from './registerCleanupTask'
 
 export function startLeakDetection() {
   if (isIE()) {
     return
   }
-  wrappedListeners = {}
+
+  let wrappedListeners: {
+    [key: string]: Map<EventListenerOrEventListenerObject | null, EventListenerOrEventListenerObject | null>
+  } = {}
 
   // eslint-disable-next-line @typescript-eslint/unbound-method
-  originalAddEventListener = EventTarget.prototype.addEventListener
+  const originalAddEventListener = EventTarget.prototype.addEventListener
   // eslint-disable-next-line @typescript-eslint/unbound-method
-  originalRemoveEventListener = EventTarget.prototype.removeEventListener
+  const originalRemoveEventListener = EventTarget.prototype.removeEventListener
 
   EventTarget.prototype.addEventListener = function (event, listener, options) {
     if (!wrappedListeners[event]) {
@@ -32,15 +30,18 @@ export function startLeakDetection() {
     wrappedListeners[event]?.delete(listener)
     return originalRemoveEventListener.call(this, event, wrappedListener || listener, options)
   }
+
+  registerCleanupTask(() => {
+    EventTarget.prototype.addEventListener = originalAddEventListener
+    EventTarget.prototype.removeEventListener = originalRemoveEventListener
+    wrappedListeners = {}
+  })
 }
 
 export function stopLeakDetection() {
   if (isIE()) {
     return
   }
-  EventTarget.prototype.addEventListener = originalAddEventListener
-  EventTarget.prototype.removeEventListener = originalRemoveEventListener
-  wrappedListeners = {}
 }
 
 function withLeakDetection(eventName: string, listener: EventListener) {
diff --git a/packages/core/test/registerCleanupTask.ts b/packages/core/test/registerCleanupTask.ts
index 29c00403db..fcc3ad459a 100644
--- a/packages/core/test/registerCleanupTask.ts
+++ b/packages/core/test/registerCleanupTask.ts
@@ -1,7 +1,7 @@
 const cleanupTasks: Array<() => void> = []
 
 export function registerCleanupTask(task: () => void) {
-  cleanupTasks.push(task)
+  cleanupTasks.unshift(task)
 }
 
 afterEach(() => {
diff --git a/packages/rum-core/src/domain/error/trackReportError.spec.ts b/packages/rum-core/src/domain/error/trackReportError.spec.ts
index c5a477d3b3..095897b501 100644
--- a/packages/rum-core/src/domain/error/trackReportError.spec.ts
+++ b/packages/rum-core/src/domain/error/trackReportError.spec.ts
@@ -7,6 +7,7 @@ import {
   mockClock,
   mockCspEventListener,
   mockReportingObserver,
+  registerCleanupTask,
 } from '@datadog/browser-core/test'
 import { mockRumConfiguration } from '../../../test'
 import type { RumConfiguration } from '../configuration'
@@ -27,13 +28,12 @@ describe('trackReportError', () => {
     notifyLog = jasmine.createSpy('notifyLog')
     reportingObserver = mockReportingObserver()
     subscription = errorObservable.subscribe(notifyLog)
-    cspEventListener = mockCspEventListener()
     clock = mockClock()
-  })
-
-  afterEach(() => {
-    subscription.unsubscribe()
-    clock.cleanup()
+    registerCleanupTask(() => {
+      subscription.unsubscribe()
+      clock.cleanup()
+    })
+    cspEventListener = mockCspEventListener()
   })
 
   it('should track reports', () => {