1 files changed, 27 insertions, 0 deletions
diff --git a/browser/components/sessionstore/test/browser_528776.js b/browser/components/sessionstore/test/browser_528776.js
new file mode 100644
index 0000000000..37b76a766d
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_528776.js
@@ -0,0 +1,27 @@
+function browserWindowsCount(expected) {
+  var count = 0;
+  for (let win of Services.wm.getEnumerator("navigator:browser")) {
+    if (!win.closed) {
+      ++count;
+    }
+  }
+  is(
+    count,
+    expected,
+    "number of open browser windows according to nsIWindowMediator"
+  );
+  is(
+    JSON.parse(ss.getBrowserState()).windows.length,
+    expected,
+    "number of open browser windows according to getBrowserState"
+  );
+}
+
+add_task(async function () {
+  browserWindowsCount(1);
+
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+  browserWindowsCount(2);
+  await BrowserTestUtils.closeWindow(win);
+  browserWindowsCount(1);
+});