--- a/mail/test/mozmill/quick-filter-bar/test-display-issues.js
+++ b/mail/test/mozmill/quick-filter-bar/test-display-issues.js
@@ -55,26 +55,28 @@ function setupModule(module) {
   wh.installInto(module);
   let qfb = collector.getModule('quick-filter-bar-helper');
   qfb.installInto(module);
 
   folder = create_folder("QuickFilterBarDisplayIssues");
   be_in_folder(folder);
 }
 
+function wait_for_resize(width) {
+  mc.waitForEval("subject.outerWidth == " + width, 1000, 50, mc.window);
+}
+
 function resize_to(width, height) {
   mark_action("test", "resize_to", [width, "x", height]);
   mc.window.resizeTo(width, height);
   // Give the event loop a spin in order to let the reality of an asynchronously
   //  interacting window manager have its impact.  This still may not be
   //  sufficient.
   mc.sleep(0);
-  mc.waitForEval("subject.outerWidth == " + width + " && " +
-                 " subject.outerHeight == " + height,
-                 1000, 50, mc.window);
+  wait_for_resize(width);
 }
 
 function collapse_folder_pane(shouldBeCollapsed) {
   mark_action("test", "collapse_folder_pane",
               [shouldBeCollapsed]);
   mc.e("folderpane_splitter").setAttribute("state",
                                            shouldBeCollapsed ? "collapsed"
                                                              : "open");
@@ -100,25 +102,33 @@ function test_buttons_collapse_and_expan
     mark_action("test", "log_window_state",
                 [aWhen,
                  "location:", mc.window.screenX, mc.window.screenY,
                  "dims:", mc.window.outerWidth, mc.window.outerHeight,
                  "Collapsy bar width:", qfbCollapsy.clientWidth,
                  "shrunk?", qfbCollapsy.getAttribute("shrink")]);
   }
 
-  function assertCollapsed() {
+  function assertCollapsed(width) {
+    // It's possible the window hasn't actually resized yet, so double-check and
+    // spin if needed.
+    wait_for_resize(width);
+
     // The bar should be shrunken and the button should be the same size as its
     // image!
     if (qfbCollapsy.getAttribute("shrink") != "true")
       throw new Error("The collapsy bar should be shrunk!");
     if (qfbExemplarLabel.clientWidth != 0)
       throw new Error("The exemplar label should be collapsed!");
   }
-  function assertExpanded() {
+  function assertExpanded(width) {
+    // It's possible the window hasn't actually resized yet, so double-check and
+    // spin if needed.
+    wait_for_resize(width);
+
     // The bar should not be shrunken and the button should be smaller than its
     // label!
     if (qfbCollapsy.hasAttribute("shrink"))
       throw new Error("The collapsy bar should not be shrunk!");
     if (qfbExemplarLabel.clientWidth == 0)
       throw new Error("The exemplar label should not be collapsed!");
   }
 
@@ -127,33 +137,33 @@ function test_buttons_collapse_and_expan
   // -- GIANT!
   resize_to(1200, 600);
   // Right, so resizeTo caps us at the display size limit, so we may end up
   // smaller than we want.  So let's turn off the folder pane too.
   collapse_folder_pane(true);
   // spin the event loop once
   mc.sleep(0);
   logState("giant");
-  assertExpanded();
+  assertExpanded(1200);
 
   // -- tiny.
   collapse_folder_pane(false);
   resize_to(600, 600);
   // spin the event loop once
   mc.sleep(0);
   logState("tiny");
-  assertCollapsed();
+  assertCollapsed(600);
 
   // -- GIANT again!
   resize_to(1200, 600);
   collapse_folder_pane(true);
   // spin the event loop once
   mc.sleep(0);
   logState("giant again!");
-  assertExpanded();
+  assertExpanded(1200);
 }
 
 function teardownModule() {
   // restore window to nominal dimensions; saving was not working out
   //  See also: message-header/test-message-header.js if we change the
   //            default window size.
   resize_to(1024, 768);
   collapse_folder_pane(false);