new file mode 100644
--- /dev/null
+++ b/netwerk/test/unit/test_channel_priority.js
@@ -0,0 +1,91 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+/* jshint esnext:true, globalstrict:true, moz:true, undef:true, unused:true */
+/* globals Cu, Ci, Assert, run_next_test, add_test, do_register_cleanup */
+/* globals runningInParent, do_send_remote_message */
+/* globals ChannelListener */
+
+'use strict';
+
+/* globals NetUtil*/
+Cu.import('resource://gre/modules/NetUtil.jsm');
+/* globals HttpServer */
+Cu.import('resource://testing-common/httpd.js');
+
+let httpserver;
+let port;
+
+function startHttpServer() {
+  httpserver = new HttpServer();
+
+  httpserver.registerPathHandler('/resource', (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, 'OK');
+    response.setHeader('Content-Type', 'text/plain', false);
+    response.setHeader('Cache-Control', 'no-cache', false);
+    response.bodyOutputStream.write("data", 4);
+  });
+
+  httpserver.registerPathHandler('/redirect', (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 302, 'Redirect');
+    response.setHeader('Location', '/resource', false);
+    response.setHeader('Cache-Control', 'no-cache', false);
+  });
+
+  httpserver.start(-1);
+  port = httpserver.identity.primaryPort;
+}
+
+function stopHttpServer() {
+  httpserver.stop(()=>{});
+}
+
+function makeRequest(uri) {
+  let requestChannel = NetUtil.newChannel({uri, loadUsingSystemPrincipal: true});
+  requestChannel.QueryInterface(Ci.nsISupportsPriority);
+  requestChannel.priority = Ci.nsISupportsPriority.PRIORITY_HIGHEST;
+  requestChannel.asyncOpen2(new ChannelListener(checkResponse, requestChannel));
+}
+
+function checkResponse(request, buffer, requestChannel) {
+  requestChannel.QueryInterface(Ci.nsISupportsPriority);
+  Assert.equal(requestChannel.priority, Ci.nsISupportsPriority.PRIORITY_HIGHEST);
+
+  // the response channel can be different (if it was redirected)
+  let responseChannel = request.QueryInterface(Ci.nsISupportsPriority);
+  Assert.equal(responseChannel.priority, Ci.nsISupportsPriority.PRIORITY_HIGHEST);
+
+  run_next_test();
+}
+
+add_test(function test_regular_request() {
+  makeRequest(`http://localhost:${port}/resource`);
+});
+
+add_test(function test_redirect() {
+  makeRequest(`http://localhost:${port}/redirect`);
+});
+
+function run_test() { // jshint ignore:line
+  if (!runningInParent) {
+    // add a task to report test finished to parent process at the end of test queue,
+    // since do_register_cleanup is not available in child xpcshell test script.
+    add_test(function () {
+      do_send_remote_message('finished');
+      run_next_test();
+    });
+
+    // waiting for parent process to assign server port via configPort()
+    return;
+  }
+
+  startHttpServer();
+  do_register_cleanup(stopHttpServer);
+  run_next_test();
+}
+
+// This is used by unit_ipc/test_channel_priority_wrap.js for e10s XPCShell test
+function configPort(serverPort) { // jshint ignore:line
+  port = serverPort;
+  run_next_test();
+}

--- a/netwerk/test/unit/xpcshell.ini
+++ b/netwerk/test/unit/xpcshell.ini
@@ -377,8 +377,9 @@ skip-if = os == "android"
 [test_bug1279246.js]
 [test_throttlequeue.js]
 [test_throttlechannel.js]
 [test_throttling.js]
 [test_separate_connections.js]
 [test_rusturl.js]
 [test_trackingProtection_annotateChannels.js]
 [test_race_cache_network.js]
+[test_channel_priority.js]

new file mode 100644
--- /dev/null
+++ b/netwerk/test/unit_ipc/test_channel_priority_wrap.js
@@ -0,0 +1,50 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+/* jshint esnext:true, globalstrict:true, moz:true, undef:true, unused:true */
+/* globals Cu, do_register_cleanup, do_test_finished */
+/* globals run_test_in_child, sendCommand, do_await_remote_message */
+
+'use strict';
+
+/* globals HttpServer */
+Cu.import('resource://testing-common/httpd.js');
+
+let httpserver;
+let port;
+
+function startHttpServer() {
+  httpserver = new HttpServer();
+
+  httpserver.registerPathHandler('/resource', (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, 'OK');
+    response.setHeader('Content-Type', 'text/plain', false);
+    response.setHeader('Cache-Control', 'no-cache', false);
+    response.bodyOutputStream.write("data", 4);
+  });
+
+  httpserver.registerPathHandler('/redirect', (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 302, 'Redirect');
+    response.setHeader('Location', '/resource', false);
+    response.setHeader('Cache-Control', 'no-cache', false);
+  });
+
+  httpserver.start(-1);
+  port = httpserver.identity.primaryPort;
+}
+
+function stopHttpServer() {
+  httpserver.stop(()=>{});
+}
+
+function run_test() { // jshint ignore:line
+  do_register_cleanup(stopHttpServer);
+
+  run_test_in_child('../unit/test_channel_priority.js', () => {
+    startHttpServer();
+    sendCommand(`configPort(${port});`);
+    do_await_remote_message('finished').then(() => {
+      do_test_finished();
+    });
+  });
+}

--- a/netwerk/test/unit_ipc/xpcshell.ini
+++ b/netwerk/test/unit_ipc/xpcshell.ini
@@ -50,16 +50,17 @@ support-files =
   !/netwerk/test/unit/data/test_readline4.txt
   !/netwerk/test/unit/data/test_readline5.txt
   !/netwerk/test/unit/data/test_readline6.txt
   !/netwerk/test/unit/data/test_readline7.txt
   !/netwerk/test/unit/data/test_readline8.txt
   !/netwerk/test/unit/data/signed_win.exe
   !/netwerk/test/unit/test_alt-data_simple.js
   !/netwerk/test/unit/test_alt-data_stream.js
+  !/netwerk/test/unit/test_channel_priority.js
 
 [test_bug528292_wrap.js]
 [test_bug248970_cookie_wrap.js]
 [test_cacheflags_wrap.js]
 [test_cache_jar_wrap.js]
 [test_channel_close_wrap.js]
 [test_cookie_header_wrap.js]
 [test_cookiejars_wrap.js]
@@ -94,8 +95,9 @@ skip-if = true
 [test_reply_without_content_type_wrap.js]
 [test_getHost_wrap.js]
 [test_alt-data_simple_wrap.js]
 [test_alt-data_stream_wrap.js]
 [test_original_sent_received_head_wrap.js]
 [test_channel_id.js]
 [test_trackingProtection_annotateChannels_wrap1.js]
 [test_trackingProtection_annotateChannels_wrap2.js]
+[test_channel_priority_wrap.js]