diff --git a/netwerk/test/httpserver/test/head_utils.js b/netwerk/test/httpserver/test/head_utils.js
index 21f61511740f..841da9b326dd 100644
--- a/netwerk/test/httpserver/test/head_utils.js
+++ b/netwerk/test/httpserver/test/head_utils.js
@@ -77,7 +77,7 @@ function fileContents(file)
  *   an Iterator which returns each line from data in turn; note that this
  *   includes a final empty line if data ended with a CRLF
  */
-function LineIterator(data)
+function* LineIterator(data)
 {
   var start = 0, index = 0;
   do
@@ -107,7 +107,7 @@ function LineIterator(data)
 function expectLines(iter, expectedLines)
 {
   var index = 0;
-  for (var line in iter)
+  for (var line of iter)
   {
     if (expectedLines.length == index)
       throw "Error: got more than " + expectedLines.length + " expected lines!";
@@ -155,9 +155,9 @@ function writeDetails(request, response)
  */
 function skipHeaders(iter)
 {
-  var line = iter.next();
+  var line = iter.next().value;
   while (line !== "")
-    line = iter.next();
+    line = iter.next().value;
 }
 
 /**
diff --git a/netwerk/test/httpserver/test/test_host.js b/netwerk/test/httpserver/test/test_host.js
index 503a04fef082..8dfa3eb6b5d0 100644
--- a/netwerk/test/httpserver/test/test_host.js
+++ b/netwerk/test/httpserver/test/test_host.js
@@ -267,7 +267,7 @@ function check400(data)
   var iter = LineIterator(data);
 
   // Status-Line
-  var firstLine = iter.next();
+  var { value: firstLine } = iter.next();
   do_check_eq(firstLine.substring(0, HTTP_400_LEADER_LENGTH), HTTP_400_LEADER);
 }
 
@@ -296,7 +296,7 @@ function check10(data)
   var iter = LineIterator(data);
 
   // Status-Line
-  do_check_eq(iter.next(), "HTTP/1.0 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.0 200 TEST PASSED");
 
   skipHeaders(iter);
 
@@ -395,7 +395,7 @@ function check11goodHost(data)
   var iter = LineIterator(data);
 
   // Status-Line
-  do_check_eq(iter.next(), "HTTP/1.1 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.1 200 TEST PASSED");
 
   skipHeaders(iter);
 
@@ -432,7 +432,7 @@ function check11ipHost(data)
   var iter = LineIterator(data);
 
   // Status-Line
-  do_check_eq(iter.next(), "HTTP/1.1 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.1 200 TEST PASSED");
 
   skipHeaders(iter);
 
@@ -517,7 +517,7 @@ function check10ip(data)
   var iter = LineIterator(data);
 
   // Status-Line
-  do_check_eq(iter.next(), "HTTP/1.0 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.0 200 TEST PASSED");
 
   skipHeaders(iter);
 
@@ -554,7 +554,7 @@ function check11goodHostWackyPort(data)
   var iter = LineIterator(data);
 
   // Status-Line
-  do_check_eq(iter.next(), "HTTP/1.1 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.1 200 TEST PASSED");
 
   skipHeaders(iter);
 
diff --git a/netwerk/test/httpserver/test/test_request_line_split_in_two_packets.js b/netwerk/test/httpserver/test/test_request_line_split_in_two_packets.js
index b1a863f48550..d4496944d959 100644
--- a/netwerk/test/httpserver/test/test_request_line_split_in_two_packets.js
+++ b/netwerk/test/httpserver/test/test_request_line_split_in_two_packets.js
@@ -65,7 +65,7 @@ function checkVeryLongRequestLine(data)
   print("iter object: " + iter);
 
   // Status-Line
-  do_check_eq(iter.next(), "HTTP/1.1 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.1 200 TEST PASSED");
 
   skipHeaders(iter);
 
@@ -112,7 +112,7 @@ function checkLotsOfLeadingBlankLines(data)
   print("data length: " + data.length);
   print("iter object: " + iter);
 
-  do_check_eq(iter.next(), "HTTP/1.1 200 TEST PASSED");
+  do_check_eq(iter.next().value, "HTTP/1.1 200 TEST PASSED");
 
   skipHeaders(iter);
 
diff --git a/netwerk/test/httpserver/test/test_seizepower.js b/netwerk/test/httpserver/test/test_seizepower.js
index f2d9e32c1c1d..de42fc6925c2 100644
--- a/netwerk/test/httpserver/test/test_seizepower.js
+++ b/netwerk/test/httpserver/test/test_seizepower.js
@@ -157,7 +157,7 @@ var data1 = "GET /called-too-late HTTP/1.0\r\n" +
        "\r\n";
 function checkTooLate(data)
 {
-  do_check_eq(LineIterator(data).next(), "too-late passed");
+  do_check_eq(LineIterator(data).next().value, "too-late passed");
 }
 
 var data2 = "GET /exceptions HTTP/1.0\r\n" +
@@ -178,5 +178,5 @@ var data4 = "GET /seize-after-async HTTP/1.0\r\n" +
        "\r\n";
 function checkSeizeAfterAsync(data)
 {
-  do_check_eq(LineIterator(data).next(), "HTTP/1.0 200 async seizure pass");
+  do_check_eq(LineIterator(data).next().value, "HTTP/1.0 200 async seizure pass");
 }
diff --git a/netwerk/test/unit/test_backgroundfilesaver.js b/netwerk/test/unit/test_backgroundfilesaver.js
index a545f596fd4e..46ba92c4257d 100644
--- a/netwerk/test/unit/test_backgroundfilesaver.js
+++ b/netwerk/test/unit/test_backgroundfilesaver.js
@@ -262,7 +262,7 @@ add_task(function test_setup()
   })
 });
 
-add_task(function test_normal()
+add_task(function* test_normal()
 {
   // This test demonstrates the most basic use case.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -296,7 +296,7 @@ add_task(function test_normal()
   destFile.remove(false);
 });
 
-add_task(function test_combinations()
+add_task(function* test_combinations()
 {
   let initialFile = getTempFile(TEST_FILE_NAME_1);
   let renamedFile = getTempFile(TEST_FILE_NAME_2);
@@ -403,7 +403,7 @@ add_task(function test_combinations()
   }
 });
 
-add_task(function test_setTarget_after_close_stream()
+add_task(function* test_setTarget_after_close_stream()
 {
   // This test checks the case where we close the output stream before we call
   // the setTarget method.  All the data should be buffered and written anyway.
@@ -437,7 +437,7 @@ add_task(function test_setTarget_after_close_stream()
   destFile.remove(false);
 });
 
-add_task(function test_setTarget_fast()
+add_task(function* test_setTarget_fast()
 {
   // This test checks a fast rename of the target file.
   let destFile1 = getTempFile(TEST_FILE_NAME_1);
@@ -460,7 +460,7 @@ add_task(function test_setTarget_fast()
   destFile2.remove(false);
 });
 
-add_task(function test_setTarget_multiple()
+add_task(function* test_setTarget_multiple()
 {
   // This test checks multiple renames of the target file.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -485,7 +485,7 @@ add_task(function test_setTarget_multiple()
   destFile.remove(false);
 });
 
-add_task(function test_enableAppend()
+add_task(function* test_enableAppend()
 {
   // This test checks append mode with hashing disabled.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -513,7 +513,7 @@ add_task(function test_enableAppend()
   destFile.remove(false);
 });
 
-add_task(function test_enableAppend_setTarget_fast()
+add_task(function* test_enableAppend_setTarget_fast()
 {
   // This test checks a fast rename of the target file in append mode.
   let destFile1 = getTempFile(TEST_FILE_NAME_1);
@@ -550,7 +550,7 @@ add_task(function test_enableAppend_setTarget_fast()
   destFile1.remove(false);
 });
 
-add_task(function test_enableAppend_hash()
+add_task(function* test_enableAppend_hash()
 {
   // This test checks append mode, also verifying that the computed hash
   // includes the contents of the existing data.
@@ -582,7 +582,7 @@ add_task(function test_enableAppend_hash()
   destFile.remove(false);
 });
 
-add_task(function test_finish_only()
+add_task(function* test_finish_only()
 {
   // This test checks creating the object and doing nothing.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -595,7 +595,7 @@ add_task(function test_finish_only()
   yield completionPromise;
 });
 
-add_task(function test_empty()
+add_task(function* test_empty()
 {
   // This test checks we still create an empty file when no data is fed.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -617,7 +617,7 @@ add_task(function test_empty()
   destFile.remove(false);
 });
 
-add_task(function test_empty_hash()
+add_task(function* test_empty_hash()
 {
   // This test checks the hash of an empty file, both in normal and append mode.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -646,7 +646,7 @@ add_task(function test_empty_hash()
   destFile.remove(false);
 });
 
-add_task(function test_invalid_hash()
+add_task(function* test_invalid_hash()
 {
   let saver = new BackgroundFileSaverStreamListener();
   let completionPromise = promiseSaverComplete(saver);
@@ -676,7 +676,7 @@ add_task(function test_invalid_hash()
   } catch (ex if ex.result == Cr.NS_ERROR_FAILURE) { }
 });
 
-add_task(function test_signature()
+add_task(function* test_signature()
 {
   // Check that we get a signature if the saver is finished.
   let destFile = getTempFile(TEST_FILE_NAME_1);
@@ -704,7 +704,7 @@ add_task(function test_signature()
   destFile.remove(false);
 });
 
-add_task(function test_signature_not_enabled()
+add_task(function* test_signature_not_enabled()
 {
   // Check that we get a signature if the saver is finished on Windows.
   let destFile = getTempFile(TEST_FILE_NAME_1);
diff --git a/netwerk/test/unit/test_bug826063.js b/netwerk/test/unit/test_bug826063.js
index 233e13a9e350..f54fb2c298ff 100644
--- a/netwerk/test/unit/test_bug826063.js
+++ b/netwerk/test/unit/test_bug826063.js
@@ -25,7 +25,7 @@ LoadContext.prototype = {
   getInterface: XPCOMUtils.generateQI([Ci.nsILoadContext])
 };
 
-function getChannels() {
+function* getChannels() {
   for (let u of URIs) {
     yield NetUtil.newChannel({
       uri: u,
diff --git a/netwerk/test/unit/test_cache_jar.js b/netwerk/test/unit/test_cache_jar.js
index 126e811f86e1..5367831ab300 100644
--- a/netwerk/test/unit/test_cache_jar.js
+++ b/netwerk/test/unit/test_cache_jar.js
@@ -47,12 +47,10 @@ var fourthTests = [
   [0, false, 1, 1], [0, true, 1, 0], [1, false, 1, 0], [1, true, 1, 0]
 ];
 
-function run_all_tests() {
+async function run_all_tests() {
   for (let test of firstTests) {
     handlers_called = 0;
-    var chan = makeChan(URL, test[0], test[1], test[2]);
-    chan.asyncOpen2(new ChannelListener(doneFirstLoad, test[3]));
-    yield undefined;
+    await test_channel(...test);
   }
 
   // We can't easily cause webapp data to be cleared from the child process, so skip
@@ -68,9 +66,7 @@ function run_all_tests() {
 
   for (let test of secondTests) {
     handlers_called = 0;
-    var chan = makeChan(URL, test[0], test[1], test[2]);
-    chan.asyncOpen2(new ChannelListener(doneFirstLoad, test[3]));
-    yield undefined;
+    await test_channel(...test);
   }
 
   Services.obs.notifyObservers(null, "clear-origin-attributes-data", attrs_notInBrowser);
@@ -78,9 +74,7 @@ function run_all_tests() {
 
   for (let test of thirdTests) {
     handlers_called = 0;
-    var chan = makeChan(URL, test[0], test[1], test[2]);
-    chan.asyncOpen2(new ChannelListener(doneFirstLoad, test[3]));
-    yield undefined;
+    await test_channel(...test);
   }
 
   let attrs_userContextId = JSON.stringify({ userContextId: 1 });
@@ -88,13 +82,10 @@ function run_all_tests() {
 
   for (let test of fourthTests) {
     handlers_called = 0;
-    var chan = makeChan(URL, test[0], test[1], test[2]);
-    chan.asyncOpen2(new ChannelListener(doneFirstLoad, test[3]));
-    yield undefined;
+    await test_channel(...test);
   }
 }
 
-var gTests;
 function run_test() {
   do_get_profile();
   if (!newCacheBackEndUsed()) {
@@ -105,22 +96,26 @@ function run_test() {
   httpserv = new HttpServer();
   httpserv.registerPathHandler("/cached", cached_handler);
   httpserv.start(-1);
-  gTests = run_all_tests();
-  gTests.next();
+  run_all_tests().then(() => {
+    do_test_finished();
+  });
 }
 
-function doneFirstLoad(req, buffer, expected) {
+function test_channel(appId, inIsolatedMozBrowser, userContextId, expected) {
+  return new Promise(resolve => {
+    var chan = makeChan(URL, appId, inIsolatedMozBrowser, userContextId);
+    chan.asyncOpen2(new ChannelListener(doneFirstLoad.bind(null, resolve), expected));
+  });
+}
+
+function doneFirstLoad(resolve, req, buffer, expected) {
   // Load it again, make sure it hits the cache
   var oa = req.loadInfo.originAttributes;
   var chan = makeChan(URL, oa.appId, oa.isInIsolatedMozBrowserElement, oa.userContextId);
-  chan.asyncOpen2(new ChannelListener(doneSecondLoad, expected));
+  chan.asyncOpen2(new ChannelListener(doneSecondLoad.bind(null, resolve), expected));
 }
 
-function doneSecondLoad(req, buffer, expected) {
+function doneSecondLoad(resolve, req, buffer, expected) {
   do_check_eq(handlers_called, expected);
-  try {
-    gTests.next();
-  } catch (x) {
-    do_test_finished();
-  }
+  resolve();
 }