--- a/accessible/tests/browser/browser_shutdown_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_acc_reference.js
@@ -45,17 +45,17 @@ add_task(async function() {
 
   accService = null;
   ok(!accService, "Service is removed");
 
   // Force garbage collection that should not trigger shutdown because there is
   // a reference to an accessible object.
   forceGC();
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Now allow a11y service to shutdown.
   canShutdown = true;
   // Remove a reference to an accessible object.
   acc = null;
   ok(!acc, "Accessible object is removed");
 
   // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_doc_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_doc_acc_reference.js
@@ -37,17 +37,17 @@ add_task(async function() {
 
   accService = null;
   ok(!accService, "Service is removed");
 
   // Force garbage collection that should not trigger shutdown because there is
   // a reference to an accessible document.
   forceGC();
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Now allow a11y service to shutdown.
   canShutdown = true;
   // Remove a reference to an accessible document.
   docAcc = null;
   ok(!docAcc, "Accessible document is removed");
 
   // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_multi_acc_reference_doc.js
+++ b/accessible/tests/browser/browser_shutdown_multi_acc_reference_doc.js
@@ -48,26 +48,26 @@ add_task(async function() {
 
   accService = null;
   ok(!accService, "Service is removed");
 
   // Force garbage collection that should not trigger shutdown because there are
   // references to accessible objects.
   forceGC();
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Remove a reference to an accessible object.
   acc = null;
   ok(!acc, "Accessible object is removed");
   // Force garbage collection that should not trigger shutdown because there is
   // a reference to an accessible document.
   forceGC();
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Now allow a11y service to shutdown.
   canShutdown = true;
   // Remove a reference to an accessible document.
   docAcc = null;
   ok(!docAcc, "Accessible document is removed");
 
   // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_multi_acc_reference_obj.js
+++ b/accessible/tests/browser/browser_shutdown_multi_acc_reference_obj.js
@@ -48,26 +48,26 @@ add_task(async function() {
 
   accService = null;
   ok(!accService, "Service is removed");
 
   // Force garbage collection that should not trigger shutdown because there are
   // references to accessible objects.
   forceGC();
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Remove a reference to an accessible document.
   docAcc = null;
   ok(!docAcc, "Accessible document is removed");
   // Force garbage collection that should not trigger shutdown because there is
   // a reference to an accessible object.
   forceGC();
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Now allow a11y service to shutdown.
   canShutdown = true;
   // Remove a reference to an accessible object.
   acc = null;
   ok(!acc, "Accessible object is removed");
 
   // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_doc.js
+++ b/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_doc.js
@@ -57,26 +57,26 @@ add_task(async function() {
       );
 
       accService = null;
       ok(!accService, "Service is removed");
       // Force garbage collection that should not trigger shutdown because there
       // is a reference to an accessible proxy.
       forceGC();
       // Have some breathing room when removing a11y service references.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       // Remove a reference to an accessible proxy.
       acc = null;
       ok(!acc, "Accessible proxy is removed");
       // Force garbage collection that should not trigger shutdown because there is
       // a reference to an accessible document proxy.
       forceGC();
       // Have some breathing room when removing a11y service references.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       // Now allow a11y service to shutdown.
       canShutdown = true;
       // Remove a last reference to an accessible document proxy.
       docAcc = null;
       ok(!docAcc, "Accessible document proxy is removed");
 
       // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_obj.js
+++ b/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_obj.js
@@ -57,26 +57,26 @@ add_task(async function() {
       );
 
       accService = null;
       ok(!accService, "Service is removed");
       // Force garbage collection that should not trigger shutdown because there
       // is a reference to an accessible proxy.
       forceGC();
       // Have some breathing room when removing a11y service references.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       // Remove a reference to an accessible document proxy.
       docAcc = null;
       ok(!docAcc, "Accessible document proxy is removed");
       // Force garbage collection that should not trigger shutdown because there is
       // a reference to an accessible proxy.
       forceGC();
       // Have some breathing room when removing a11y service references.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       // Now allow a11y service to shutdown.
       canShutdown = true;
       // Remove a last reference to an accessible proxy.
       acc = null;
       ok(!acc, "Accessible proxy is removed");
 
       // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_multi_reference.js
+++ b/accessible/tests/browser/browser_shutdown_multi_reference.js
@@ -40,17 +40,17 @@ add_task(async function() {
   // Remove first a11y service reference.
   accService1 = null;
   ok(!accService1, "Service is removed");
   // Force garbage collection that should not trigger shutdown because there is
   // another reference.
   forceGC();
 
   // Have some breathing room when removing a11y service references.
-  await new Promise(resolve => executeSoon(resolve));
+  await TestUtils.waitForTick();
 
   // Now allow a11y service to shutdown.
   canShutdown = true;
   // Remove last a11y service reference.
   accService2 = null;
   ok(!accService2, "Service is removed");
   // Force garbage collection that should trigger shutdown.
   forceGC();

--- a/accessible/tests/browser/browser_shutdown_parent_own_reference.js
+++ b/accessible/tests/browser/browser_shutdown_parent_own_reference.js
@@ -73,17 +73,17 @@ add_task(async function() {
       // Remove a11y service reference in content and force garbage collection.
       // This should not trigger shutdown since a11y was originally initialized by
       // the main process.
       await SpecialPowers.spawn(browser, [], () => {
         content.CommonUtils.clearAccService();
       });
 
       // Have some breathing room between a11y service shutdowns.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       info("Removing a service in parent");
       // Now allow a11y service to shutdown in content.
       contentCanShutdown = true;
       // Remove the a11y service reference in the main process.
       const [
         parentA11yShutdownObserver,
         parentA11yShutdown,

--- a/accessible/tests/browser/browser_shutdown_proxy_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_proxy_acc_reference.js
@@ -52,17 +52,17 @@ add_task(async function() {
       );
 
       accService = null;
       ok(!accService, "Service is removed");
       // Force garbage collection that should not trigger shutdown because there
       // is a reference to an accessible proxy.
       forceGC();
       // Have some breathing room when removing a11y service references.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       // Now allow a11y service to shutdown.
       canShutdown = true;
       // Remove a last reference to an accessible proxy.
       divAcc = null;
       ok(!divAcc, "Accessible proxy is removed");
 
       // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_proxy_doc_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_proxy_doc_acc_reference.js
@@ -54,17 +54,17 @@ add_task(async function() {
       );
 
       accService = null;
       ok(!accService, "Service is removed");
       // Force garbage collection that should not trigger shutdown because there
       // is a reference to an accessible proxy.
       forceGC();
       // Have some breathing room when removing a11y service references.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       // Now allow a11y service to shutdown.
       canShutdown = true;
       // Remove a last reference to an accessible document proxy.
       docAcc = null;
       ok(!docAcc, "Accessible document proxy is removed");
 
       // Force garbage collection that should now trigger shutdown.

--- a/accessible/tests/browser/browser_shutdown_remote_own_reference.js
+++ b/accessible/tests/browser/browser_shutdown_remote_own_reference.js
@@ -151,17 +151,17 @@ add_task(async function() {
             MainProcess: false,
             PlatformAPI: false,
           },
           "Accessibility service consumers in content are correct."
         )
       );
 
       // Have some breathing room between a11y service shutdowns.
-      await new Promise(resolve => executeSoon(resolve));
+      await TestUtils.waitForTick();
 
       info("Removing a service in content");
       // Now allow a11y service to shutdown in content.
       contentCanShutdown = true;
       [
         contentConsumersChangedObserver,
         contentConsumersChanged,
       ] = accConsumersChanged(browser);