1 files changed, 81 insertions, 0 deletions
diff --git a/layout/base/tests/browser_bug1791083.js b/layout/base/tests/browser_bug1791083.js
new file mode 100644
index 0000000000..e68a723c4e
--- /dev/null
+++ b/layout/base/tests/browser_bug1791083.js
@@ -0,0 +1,81 @@
+/* Any copyright is dedicated to the Public Domain.
+    http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const URL =
+  "data:text/html," +
+  "<style> a:hover {background-color: black}</style>" +
+  "<body style='width:100px;height:100px'>" +
+  "<a href='http://www.example.com'>Click Me</a>" +
+  "</body>";
+
+function isAnchorHovered(win) {
+  return SpecialPowers.spawn(
+    win.gBrowser.selectedBrowser,
+    [],
+    async function () {
+      const a = content.document.querySelector("a");
+      return a.matches(":hover");
+    }
+  );
+}
+
+add_task(async function test() {
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+
+  // This bug is only reproducible if the cursor is out of the viewport, so
+  // we resize the window to ensure the cursor is out of the viewport.
+
+  // SynthesizeMouse isn't sufficient because it only synthesizes
+  // mouse events without actually moving the cursor permanently to a
+  // new location.
+  newWin.resizeTo(50, 50);
+
+  BrowserTestUtils.startLoadingURIString(newWin.gBrowser.selectedBrowser, URL);
+  await BrowserTestUtils.browserLoaded(newWin.gBrowser.selectedBrowser);
+
+  await SpecialPowers.spawn(
+    newWin.gBrowser.selectedBrowser,
+    [],
+    async function () {
+      const a = content.document.querySelector("a");
+      await EventUtils.synthesizeMouseAtCenter(
+        a,
+        { type: "mousemove" },
+        content
+      );
+    }
+  );
+
+  // We've hovered the anchor element.
+  let anchorHovered = await isAnchorHovered(newWin);
+  ok(anchorHovered, "Anchor should be hovered");
+
+  let locationChange = BrowserTestUtils.waitForLocationChange(newWin.gBrowser);
+
+  // Click the anchor to navigate away
+  await SpecialPowers.spawn(
+    newWin.gBrowser.selectedBrowser,
+    [],
+    async function () {
+      const a = content.document.querySelector("a");
+      await EventUtils.synthesizeMouseAtCenter(
+        a,
+        { type: "mousedown" },
+        content
+      );
+      await EventUtils.synthesizeMouseAtCenter(a, { type: "mouseup" }, content);
+    }
+  );
+  await locationChange;
+
+  // Navigate back to the previous page which has the anchor
+  locationChange = BrowserTestUtils.waitForLocationChange(newWin.gBrowser);
+  newWin.gBrowser.selectedBrowser.goBack();
+  await locationChange;
+
+  // Hover state should be cleared upon page caching.
+  anchorHovered = await isAnchorHovered(newWin);
+  ok(!anchorHovered, "Anchor should not be hovered");
+
+  BrowserTestUtils.closeWindow(newWin);
+});