1 files changed, 76 insertions, 0 deletions
diff --git a/modules/libpref/test/unit_ipc/test_sharedMap_static_prefs.js b/modules/libpref/test/unit_ipc/test_sharedMap_static_prefs.js
new file mode 100644
index 0000000000..a8181bf2cb
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+++ b/modules/libpref/test/unit_ipc/test_sharedMap_static_prefs.js
@@ -0,0 +1,76 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// Tests that static preferences in the content process
+// correctly handle values which are different from their
+// statically-defined defaults.
+//
+// Since we can't access static preference values from JS, this tests relies on
+// assertions in debug builds to detect mismatches. The default and user
+// values of two preferences are changed (respectively) before a content
+// process is started. Once the content process is launched, the
+// preference service asserts that the values stored in all static prefs
+// match their current values as known to the preference service. If
+// there's a mismatch, the shell will crash, and the test will fail.
+//
+// For sanity, we also check that the dynamically retrieved preference
+// values in the content process match our expectations, though this is
+// not strictly part of the test.
+
+const PREF1_NAME = "dom.webcomponents.shadowdom.report_usage";
+const PREF1_VALUE = false;
+
+const PREF2_NAME = "dom.mutation-events.cssom.disabled";
+const PREF2_VALUE = true;
+
+const { XPCShellContentUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/XPCShellContentUtils.sys.mjs"
+);
+
+XPCShellContentUtils.init(this);
+
+const { prefs } = Services;
+const defaultPrefs = prefs.getDefaultBranch("");
+
+add_task(async function test_sharedMap_static_prefs() {
+  equal(
+    prefs.getBoolPref(PREF1_NAME),
+    PREF1_VALUE,
+    `Expected initial value for ${PREF1_NAME}`
+  );
+  equal(
+    prefs.getBoolPref(PREF2_NAME),
+    PREF2_VALUE,
+    `Expected initial value for ${PREF2_NAME}`
+  );
+
+  defaultPrefs.setBoolPref(PREF1_NAME, !PREF1_VALUE);
+  prefs.setBoolPref(PREF2_NAME, !PREF2_VALUE);
+
+  equal(
+    prefs.getBoolPref(PREF1_NAME),
+    !PREF1_VALUE,
+    `Expected updated value for ${PREF1_NAME}`
+  );
+  equal(
+    prefs.getBoolPref(PREF2_NAME),
+    !PREF2_VALUE,
+    `Expected updated value for ${PREF2_NAME}`
+  );
+
+  let contentPage = await XPCShellContentUtils.loadContentPage("about:blank", {
+    remote: true,
+  });
+  registerCleanupFunction(() => contentPage.close());
+
+  /* eslint-disable no-shadow */
+  let values = await contentPage.spawn([[PREF1_NAME, PREF2_NAME]], prefs => {
+    return prefs.map(pref => Services.prefs.getBoolPref(pref));
+  });
+  /* eslint-enable no-shadow */
+
+  equal(values[0], !PREF1_VALUE, `Expected content value for ${PREF1_NAME}`);
+  equal(values[1], !PREF2_VALUE, `Expected content value for ${PREF2_NAME}`);
+});