2 files changed, 48 insertions, 0 deletions
diff --git a/modules/libpref/test/unit/test_backupPrefFile.js b/modules/libpref/test/unit/test_backupPrefFile.js
new file mode 100644
index 0000000000..6624443e7c
--- /dev/null
+++ b/modules/libpref/test/unit/test_backupPrefFile.js
@@ -0,0 +1,46 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Tests that we can create a backup of the preferences state to
+ * a file asynchronously.
+ */
+add_task(async function test_backupPrefFile() {
+  // Create a backup of the preferences state to a file.
+  Services.prefs.setBoolPref("test.backup", true);
+
+  let backupFilePath = PathUtils.join(PathUtils.tempDir, "prefs-backup.js");
+  let backupFile = await IOUtils.getFile(backupFilePath);
+  await Services.prefs.backupPrefFile(backupFile);
+
+  // Verify that the backup file was created and contains the expected content.
+  let backupContent = await IOUtils.read(backupFilePath, { encoding: "utf-8" });
+
+  let sawTestValue = false;
+
+  // Now parse the backup file and verify that it contains the expected
+  // preference value. We'll not worry about any of the other preferences.
+  let observer = {
+    onStringPref() {},
+    onIntPref() {},
+    onBoolPref(kind, name, value, _isSticky, _isLocked) {
+      if (name == "test.backup" && value) {
+        sawTestValue = true;
+      }
+    },
+    onError(message) {
+      Assert.ok(false, "Error while parsing backup file: " + message);
+    },
+  };
+  Services.prefs.parsePrefsFromBuffer(backupContent, observer);
+
+  Assert.ok(
+    sawTestValue,
+    "The backup file contains the expected preference value."
+  );
+
+  // Clean up the backup file.
+  await IOUtils.remove(backupFilePath);
+});
diff --git a/modules/libpref/test/unit/xpcshell.toml b/modules/libpref/test/unit/xpcshell.toml
index 6f9440d609..03cf56d21a 100644
--- a/modules/libpref/test/unit/xpcshell.toml
+++ b/modules/libpref/test/unit/xpcshell.toml
@@ -5,6 +5,8 @@ support-files = [
   "extdata/testExt.js",
 ]
 
+["test_backupPrefFile.js"]
+
 ["test_bug345529.js"]
 
 ["test_bug506224.js"]