1 files changed, 70 insertions, 0 deletions
diff --git a/toolkit/components/reader/test/browser_bug1780350_readerModeSaveScroll.js b/toolkit/components/reader/test/browser_bug1780350_readerModeSaveScroll.js
new file mode 100644
index 0000000000..76add5511e
--- /dev/null
+++ b/toolkit/components/reader/test/browser_bug1780350_readerModeSaveScroll.js
@@ -0,0 +1,70 @@
+/* eslint-disable @microsoft/sdl/no-insecure-url */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+const TEST_PATH = getRootDirectory(gTestPath).replace(
+  "chrome://mochitests/content",
+  "http://example.com"
+);
+
+// This test verifies that when a link is clicked from
+// within reader view, when navigating back to reader view
+// the previous scroll position of the page is restored.
+add_task(async function test_save_scroll_position() {
+  await BrowserTestUtils.withNewTab(
+    TEST_PATH + "readerModeArticleContainsLink.html",
+    async function (browser) {
+      let pageShownPromise = BrowserTestUtils.waitForContentEvent(
+        browser,
+        "AboutReaderContentReady"
+      );
+      let browserLoadedPromise = BrowserTestUtils.browserLoaded(browser);
+      let readerButton = document.getElementById("reader-mode-button");
+      readerButton.click();
+      await Promise.all([pageShownPromise, browserLoadedPromise]);
+      let scrollEventPromise = BrowserTestUtils.waitForContentEvent(
+        browser,
+        "scroll",
+        true
+      );
+      // Set scroll position in reader to 200px down.
+      await SpecialPowers.spawn(browser, [], async function () {
+        content.document.documentElement.scrollTop = 200;
+      });
+      await scrollEventPromise;
+
+      // Click linked page and check that scroll pos resets.
+      await SpecialPowers.spawn(browser, [], async function () {
+        let linkElement = content.document.getElementById("link");
+        linkElement.click();
+      });
+      await BrowserTestUtils.browserLoaded(browser);
+      await SpecialPowers.spawn(browser, [], async function () {
+        is(
+          content.document.documentElement.scrollTop,
+          0,
+          "vertical scroll position should reset to zero when navigating to linked page."
+        );
+        content.window.history.back();
+      });
+
+      // Navigate back to reader and check that scroll position is restored.
+      await BrowserTestUtils.browserLoaded(browser);
+      scrollEventPromise = BrowserTestUtils.waitForContentEvent(
+        browser,
+        "scroll",
+        true
+      );
+      await scrollEventPromise;
+      await SpecialPowers.spawn(browser, [], async function () {
+        let doc = content.document;
+        is(
+          doc.documentElement.scrollTop,
+          200,
+          "should restore saved scroll position when navigating back from link."
+        );
+      });
+    }
+  );
+});