diff --git a/js/xpconnect/tests/unit/head_watchdog.js b/js/xpconnect/tests/unit/head_watchdog.js
index cf006303aae8..87ec5de76910 100644
--- a/js/xpconnect/tests/unit/head_watchdog.js
+++ b/js/xpconnect/tests/unit/head_watchdog.js
@@ -95,18 +95,14 @@ function checkWatchdog(expectInterrupt, continuation) {
   });
 }
 
-var gGenerator;
-function continueTest() {
-  gGenerator.next();
-}
-
 function run_test() {
 
   // Run async.
   do_test_pending();
 
-  // Instantiate the generator and kick it off.
-  gGenerator = testBody();
-  gGenerator.next();
+  // Run the async function.
+  testBody().then(() => {
+    do_test_finished();
+  });
 }
 
diff --git a/js/xpconnect/tests/unit/test_watchdog_default.js b/js/xpconnect/tests/unit/test_watchdog_default.js
index d5dac7b6aeaf..75e8f0e7632b 100644
--- a/js/xpconnect/tests/unit/test_watchdog_default.js
+++ b/js/xpconnect/tests/unit/test_watchdog_default.js
@@ -2,11 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-function testBody() {
+async function testBody() {
   // Check that we properly implement whatever behavior is specified by the
   // default profile for this configuration.
-  checkWatchdog(isWatchdogEnabled(), continueTest);
-  yield;
-  do_test_finished();
-  yield;
+  await checkWatchdog(isWatchdogEnabled());
 }
diff --git a/js/xpconnect/tests/unit/test_watchdog_disable.js b/js/xpconnect/tests/unit/test_watchdog_disable.js
index dcdf21ce4656..45837dabaf5b 100644
--- a/js/xpconnect/tests/unit/test_watchdog_disable.js
+++ b/js/xpconnect/tests/unit/test_watchdog_disable.js
@@ -2,10 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-function testBody() {
+async function testBody() {
   setWatchdogEnabled(false);
-  checkWatchdog(false, continueTest);
-  yield;
-  do_test_finished();
-  yield;
+  await checkWatchdog(false);
 }
diff --git a/js/xpconnect/tests/unit/test_watchdog_enable.js b/js/xpconnect/tests/unit/test_watchdog_enable.js
index 8e31e1316928..234e7d76a49c 100644
--- a/js/xpconnect/tests/unit/test_watchdog_enable.js
+++ b/js/xpconnect/tests/unit/test_watchdog_enable.js
@@ -2,10 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-function testBody() {
+async function testBody() {
   setWatchdogEnabled(true);
-  checkWatchdog(true, continueTest);
-  yield;
-  do_test_finished();
-  yield;
+  await checkWatchdog(true);
 }
diff --git a/js/xpconnect/tests/unit/test_watchdog_hibernate.js b/js/xpconnect/tests/unit/test_watchdog_hibernate.js
index ce36429632f9..15d2014ed65e 100644
--- a/js/xpconnect/tests/unit/test_watchdog_hibernate.js
+++ b/js/xpconnect/tests/unit/test_watchdog_hibernate.js
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-function testBody() {
+async function testBody() {
 
   setWatchdogEnabled(true);
 
@@ -23,10 +23,11 @@ function testBody() {
   // scheduling, we should never have more than 3 seconds of inactivity without
   // hibernating. To add some padding for automation, we mandate that hibernation
   // must begin between 2 and 5 seconds from now.
-  var timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
-  timer.initWithCallback(continueTest, 10000, Ci.nsITimer.TYPE_ONE_SHOT);
-  simulateActivityCallback(false);
-  yield;
+  await new Promise(resolve => {
+    var timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+    timer.initWithCallback(resolve, 10000, Ci.nsITimer.TYPE_ONE_SHOT);
+    simulateActivityCallback(false);
+  });
 
   simulateActivityCallback(true);
   busyWait(1000); // Give the watchdog time to wake up on the condvar.
@@ -47,7 +48,4 @@ function testBody() {
   do_check_true(startHibernation > now + 2*1000*1000 - FUZZ_FACTOR);
   do_check_true(startHibernation < now + 5*1000*1000 + FUZZ_FACTOR);
   do_check_true(stopHibernation > now + 10*1000*1000 - FUZZ_FACTOR);
-
-  do_test_finished();
-  yield;
 }
diff --git a/js/xpconnect/tests/unit/test_watchdog_toggle.js b/js/xpconnect/tests/unit/test_watchdog_toggle.js
index f0d14c2dfe86..1b2c90df9d03 100644
--- a/js/xpconnect/tests/unit/test_watchdog_toggle.js
+++ b/js/xpconnect/tests/unit/test_watchdog_toggle.js
@@ -2,12 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-function testBody() {
+async function testBody() {
   var defaultBehavior = isWatchdogEnabled();
   setWatchdogEnabled(!defaultBehavior);
   setWatchdogEnabled(defaultBehavior);
-  checkWatchdog(defaultBehavior, continueTest);
-  yield;
-  do_test_finished();
-  yield;
+  await checkWatchdog(defaultBehavior);
 }