diff --git a/dom/media/tests/mochitest/test_getUserMedia_basicScreenshare.html b/dom/media/tests/mochitest/test_getUserMedia_basicScreenshare.html
index 58bd42f61e06..e7d7477eb131 100644
--- a/dom/media/tests/mochitest/test_getUserMedia_basicScreenshare.html
+++ b/dom/media/tests/mochitest/test_getUserMedia_basicScreenshare.html
@@ -23,6 +23,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=983504
    * Run a test to verify that we can complete a start and stop media playback
    * cycle for an screenshare LocalMediaStream on a video HTMLMediaElement.
    */
+  SimpleTest.expectAssertions(0, 1); // Bug 1047842
+
   runTest(function () {
     const isWinXP = navigator.userAgent.indexOf("Windows NT 5.1") != -1;
     if (IsMacOSX10_6orOlder() || isWinXP) {
diff --git a/dom/media/tests/mochitest/test_getUserMedia_basicWindowshare.html b/dom/media/tests/mochitest/test_getUserMedia_basicWindowshare.html
index 0c4aac42abd9..170af2c7adc6 100644
--- a/dom/media/tests/mochitest/test_getUserMedia_basicWindowshare.html
+++ b/dom/media/tests/mochitest/test_getUserMedia_basicWindowshare.html
@@ -23,6 +23,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=983504
    * Run a test to verify that we can complete a start and stop media playback
    * cycle for an screenshare LocalMediaStream on a video HTMLMediaElement.
    */
+  SimpleTest.expectAssertions(0, 1); // Bug 1047842
+
   runTest(function () {
     const isWinXP = navigator.userAgent.indexOf("Windows NT 5.1") != -1;
     if (IsMacOSX10_6orOlder() || isWinXP) {
diff --git a/dom/media/tests/mochitest/test_peerConnection_basicScreenshare.html b/dom/media/tests/mochitest/test_peerConnection_basicScreenshare.html
index 0e1c93fc8d7b..123175e20949 100644
--- a/dom/media/tests/mochitest/test_peerConnection_basicScreenshare.html
+++ b/dom/media/tests/mochitest/test_peerConnection_basicScreenshare.html
@@ -17,6 +17,8 @@
     title: "Basic screenshare-only peer connection"
   });
 
+  SimpleTest.expectAssertions(0, 1); // Bug 1047842
+
   var test;
   runNetworkTest(function (options) {
     const isWinXP = navigator.userAgent.indexOf("Windows NT 5.1") != -1;
diff --git a/dom/media/tests/mochitest/test_peerConnection_basicWindowshare.html b/dom/media/tests/mochitest/test_peerConnection_basicWindowshare.html
index ae8369c06b7c..37a6c86b8850 100644
--- a/dom/media/tests/mochitest/test_peerConnection_basicWindowshare.html
+++ b/dom/media/tests/mochitest/test_peerConnection_basicWindowshare.html
@@ -17,6 +17,8 @@
     title: "Basic windowshare-only peer connection"
   });
 
+  SimpleTest.expectAssertions(0, 1); // Bug 1047842
+
   var test;
   runNetworkTest(function (options) {
     const isWinXP = navigator.userAgent.indexOf("Windows NT 5.1") != -1;