diff --git a/services/sync/tests/unit/test_Observers.js b/services/sync/tests/unit/test_Observers.js
new file mode 100644
index 00000000000..c85eacf019c
--- /dev/null
+++ b/services/sync/tests/unit/test_Observers.js
@@ -0,0 +1,77 @@
+Components.utils.import("resource://services-sync/ext/Observers.js");
+
+let gSubject = {};
+
+function test_function_observer() {
+  let foo = false;
+
+  let onFoo = function(subject, data) {
+    foo = !foo;
+    do_check_eq(subject, gSubject);
+    do_check_eq(data, "some data");
+  };
+
+  Observers.add("foo", onFoo);
+  Observers.notify("foo", gSubject, "some data");
+
+  // The observer was notified after being added.
+  do_check_true(foo);
+
+  Observers.remove("foo", onFoo);
+  Observers.notify("foo");
+
+  // The observer was not notified after being removed.
+  do_check_true(foo);
+}
+
+function test_method_observer() {
+  let obj = {
+    foo: false,
+    onFoo: function(subject, data) {
+      this.foo = !this.foo;
+      do_check_eq(subject, gSubject);
+      do_check_eq(data, "some data");
+    }
+  };
+
+  // The observer is notified after being added.
+  Observers.add("foo", obj.onFoo, obj);
+  Observers.notify("foo", gSubject, "some data");
+  do_check_true(obj.foo);
+
+  // The observer is not notified after being removed.
+  Observers.remove("foo", obj.onFoo, obj);
+  Observers.notify("foo");
+  do_check_true(obj.foo);
+}
+
+function test_object_observer() {
+  let obj = {
+    foo: false,
+    observe: function(subject, topic, data) {
+      this.foo = !this.foo;
+
+      do_check_eq(subject, gSubject);
+      do_check_eq(topic, "foo");
+      do_check_eq(data, "some data");
+    }
+  };
+
+  Observers.add("foo", obj);
+  Observers.notify("foo", gSubject, "some data");
+
+  // The observer is notified after being added.
+  do_check_true(obj.foo);
+
+  Observers.remove("foo", obj);
+  Observers.notify("foo");
+
+  // The observer is not notified after being removed.
+  do_check_true(obj.foo);
+}
+
+function run_test() {
+  test_function_observer();
+  test_method_observer();
+  test_object_observer();
+}
diff --git a/services/sync/tests/unit/test_Preferences.js b/services/sync/tests/unit/test_Preferences.js
new file mode 100644
index 00000000000..105834fe8e6
--- /dev/null
+++ b/services/sync/tests/unit/test_Preferences.js
@@ -0,0 +1,354 @@
+Components.utils.import("resource://services-sync/ext/Preferences.js");
+
+function test_set_get_pref() {
+  Preferences.set("test_set_get_pref.integer", 1);
+  do_check_eq(Preferences.get("test_set_get_pref.integer"), 1);
+
+  Preferences.set("test_set_get_pref.string", "foo");
+  do_check_eq(Preferences.get("test_set_get_pref.string"), "foo");
+
+  Preferences.set("test_set_get_pref.boolean", true);
+  do_check_eq(Preferences.get("test_set_get_pref.boolean"), true);
+
+  // Clean up.
+  Preferences.resetBranch("test_set_get_pref.");
+}
+
+function test_set_get_branch_pref() {
+  let prefs = new Preferences("test_set_get_branch_pref.");
+
+  prefs.set("something", 1);
+  do_check_eq(prefs.get("something"), 1);
+  do_check_false(Preferences.has("something"));
+
+  // Clean up.
+  prefs.reset("something");
+}
+
+function test_set_get_multiple_prefs() {
+  Preferences.set({ "test_set_get_multiple_prefs.integer":  1,
+                    "test_set_get_multiple_prefs.string":   "foo",
+                    "test_set_get_multiple_prefs.boolean":  true });
+
+  let [i, s, b] = Preferences.get(["test_set_get_multiple_prefs.integer",
+                                   "test_set_get_multiple_prefs.string",
+                                   "test_set_get_multiple_prefs.boolean"]);
+
+  do_check_eq(i, 1);
+  do_check_eq(s, "foo");
+  do_check_eq(b, true);
+
+  // Clean up.
+  Preferences.resetBranch("test_set_get_multiple_prefs.");
+}
+
+function test_get_multiple_prefs_with_default_value() {
+  Preferences.set({ "test_get_multiple_prefs_with_default_value.a":  1,
+                    "test_get_multiple_prefs_with_default_value.b":  2 });
+
+  let [a, b, c] = Preferences.get(["test_get_multiple_prefs_with_default_value.a",
+                                   "test_get_multiple_prefs_with_default_value.b",
+                                   "test_get_multiple_prefs_with_default_value.c"],
+                                  0);
+
+  do_check_eq(a, 1);
+  do_check_eq(b, 2);
+  do_check_eq(c, 0);
+
+  // Clean up.
+  Preferences.resetBranch("test_get_multiple_prefs_with_default_value.");
+}
+
+function test_set_get_unicode_pref() {
+  Preferences.set("test_set_get_unicode_pref", String.fromCharCode(960));
+  do_check_eq(Preferences.get("test_set_get_unicode_pref"), String.fromCharCode(960));
+
+  // Clean up.
+  Preferences.reset("test_set_get_unicode_pref");
+}
+
+function test_set_null_pref() {
+  try {
+    Preferences.set("test_set_null_pref", null);
+    // We expect this to throw, so the test is designed to fail if it doesn't.
+    do_check_true(false);
+  }
+  catch(ex) {}
+}
+
+function test_set_undefined_pref() {
+  try {
+    Preferences.set("test_set_undefined_pref");
+    // We expect this to throw, so the test is designed to fail if it doesn't.
+    do_check_true(false);
+  }
+  catch(ex) {}
+}
+
+function test_set_unsupported_pref() {
+  try {
+    Preferences.set("test_set_unsupported_pref", new Array());
+    // We expect this to throw, so the test is designed to fail if it doesn't.
+    do_check_true(false);
+  }
+  catch(ex) {}
+}
+
+// Make sure that we can get a string pref that we didn't set ourselves
+// (i.e. that the way we get a string pref using getComplexValue doesn't
+// hork us getting a string pref that wasn't set using setComplexValue).
+function test_get_string_pref() {
+  let svc = Cc["@mozilla.org/preferences-service;1"].
+            getService(Ci.nsIPrefService).
+            getBranch("");
+  svc.setCharPref("test_get_string_pref", "a normal string");
+  do_check_eq(Preferences.get("test_get_string_pref"), "a normal string");
+
+  // Clean up.
+  Preferences.reset("test_get_string_pref");
+}
+
+function test_set_get_number_pref() {
+  Preferences.set("test_set_get_number_pref", 5);
+  do_check_eq(Preferences.get("test_set_get_number_pref"), 5);
+
+  // Non-integer values get converted to integers.
+  Preferences.set("test_set_get_number_pref", 3.14159);
+  do_check_eq(Preferences.get("test_set_get_number_pref"), 3);
+
+  // Values outside the range -(2^31-1) to 2^31-1 overflow.
+  try {
+    Preferences.set("test_set_get_number_pref", Math.pow(2, 31));
+    // We expect this to throw, so the test is designed to fail if it doesn't.
+    do_check_true(false);
+  }
+  catch(ex) {}
+
+  // Clean up.
+  Preferences.reset("test_set_get_number_pref");
+}
+
+function test_reset_pref() {
+  Preferences.set("test_reset_pref", 1);
+  Preferences.reset("test_reset_pref");
+  do_check_eq(Preferences.get("test_reset_pref"), undefined);
+}
+
+function test_reset_pref_branch() {
+  Preferences.set("test_reset_pref_branch.foo", 1);
+  Preferences.set("test_reset_pref_branch.bar", 2);
+  Preferences.resetBranch("test_reset_pref_branch.");
+  do_check_eq(Preferences.get("test_reset_pref_branch.foo"), undefined);
+  do_check_eq(Preferences.get("test_reset_pref_branch.bar"), undefined);
+}
+
+// Make sure the module doesn't throw an exception when asked to reset
+// a nonexistent pref.
+function test_reset_nonexistent_pref() {
+  Preferences.reset("test_reset_nonexistent_pref");
+}
+
+// Make sure the module doesn't throw an exception when asked to reset
+// a nonexistent pref branch.
+function test_reset_nonexistent_pref_branch() {
+  Preferences.resetBranch("test_reset_nonexistent_pref_branch.");
+}
+
+function test_observe_prefs_function() {
+  let observed = false;
+  let observer = function() { observed = !observed };
+
+  Preferences.observe("test_observe_prefs_function", observer);
+  Preferences.set("test_observe_prefs_function", "something");
+  do_check_true(observed);
+
+  Preferences.ignore("test_observe_prefs_function", observer);
+  Preferences.set("test_observe_prefs_function", "something else");
+  do_check_true(observed);
+
+  // Clean up.
+  Preferences.reset("test_observe_prefs_function");
+}
+
+function test_observe_prefs_object() {
+  let observer = {
+    observed: false,
+    observe: function() {
+      this.observed = !this.observed;
+    }
+  };
+
+  Preferences.observe("test_observe_prefs_object", observer.observe, observer);
+  Preferences.set("test_observe_prefs_object", "something");
+  do_check_true(observer.observed);
+
+  Preferences.ignore("test_observe_prefs_object", observer.observe, observer);
+  Preferences.set("test_observe_prefs_object", "something else");
+  do_check_true(observer.observed);
+
+  // Clean up.
+  Preferences.reset("test_observe_prefs_object");
+}
+
+function test_observe_prefs_nsIObserver() {
+  let observer = {
+    observed: false,
+    observe: function(subject, topic, data) {
+      this.observed = !this.observed;
+      do_check_true(subject instanceof Ci.nsIPrefBranch2);
+      do_check_eq(topic, "nsPref:changed");
+      do_check_eq(data, "test_observe_prefs_nsIObserver");
+    }
+  };
+
+  Preferences.observe("test_observe_prefs_nsIObserver", observer);
+  Preferences.set("test_observe_prefs_nsIObserver", "something");
+  do_check_true(observer.observed);
+
+  Preferences.ignore("test_observe_prefs_nsIObserver", observer);
+  Preferences.set("test_observe_prefs_nsIObserver", "something else");
+  do_check_true(observer.observed);
+
+  // Clean up.
+  Preferences.reset("test_observe_prefs_nsIObserver");
+}
+
+function test_observe_exact_pref() {
+  let observed = false;
+  let observer = function() { observed = !observed };
+
+  Preferences.observe("test_observe_exact_pref", observer);
+  Preferences.set("test_observe_exact_pref.sub-pref", "something");
+  do_check_false(observed);
+
+  // Clean up.
+  Preferences.ignore("test_observe_exact_pref", observer);
+  Preferences.reset("test_observe_exact_pref.sub-pref");
+}
+
+function test_observe_value_of_set_pref() {
+  let observer = function(newVal) { do_check_eq(newVal, "something") };
+
+  Preferences.observe("test_observe_value_of_set_pref", observer);
+  Preferences.set("test_observe_value_of_set_pref", "something");
+
+  // Clean up.
+  Preferences.ignore("test_observe_value_of_set_pref", observer);
+  Preferences.reset("test_observe_value_of_set_pref");
+}
+
+function test_observe_value_of_reset_pref() {
+  let observer = function(newVal) { do_check_true(typeof newVal == "undefined") };
+
+  Preferences.set("test_observe_value_of_reset_pref", "something");
+  Preferences.observe("test_observe_value_of_reset_pref", observer);
+  Preferences.reset("test_observe_value_of_reset_pref");
+
+  // Clean up.
+  Preferences.ignore("test_observe_value_of_reset_pref", observer);
+}
+
+function test_has_pref() {
+  do_check_false(Preferences.has("test_has_pref"));
+  Preferences.set("test_has_pref", "foo");
+  do_check_true(Preferences.has("test_has_pref"));
+
+  Preferences.set("test_has_pref.foo", "foo");
+  Preferences.set("test_has_pref.bar", "bar");
+  let [hasFoo, hasBar, hasBaz] = Preferences.has(["test_has_pref.foo",
+                                                  "test_has_pref.bar",
+                                                  "test_has_pref.baz"]);
+  do_check_true(hasFoo);
+  do_check_true(hasBar);
+  do_check_false(hasBaz);
+
+  // Clean up.
+  Preferences.resetBranch("test_has_pref");
+}
+
+function test_isSet_pref() {
+  // Use a pref that we know has a default value but no user-set value.
+  // This feels dangerous; perhaps we should create some other default prefs
+  // that we can use for testing.
+  do_check_false(Preferences.isSet("toolkit.defaultChromeURI"));
+  Preferences.set("toolkit.defaultChromeURI", "foo");
+  do_check_true(Preferences.isSet("toolkit.defaultChromeURI"));
+
+  // Clean up.
+  Preferences.reset("toolkit.defaultChromeURI");
+}
+
+function test_lock_prefs() {
+  // Use a pref that we know has a default value.
+  // This feels dangerous; perhaps we should create some other default prefs
+  // that we can use for testing.
+  do_check_false(Preferences.locked("toolkit.defaultChromeURI"));
+  Preferences.lock("toolkit.defaultChromeURI");
+  do_check_true(Preferences.locked("toolkit.defaultChromeURI"));
+  Preferences.unlock("toolkit.defaultChromeURI");
+  do_check_false(Preferences.locked("toolkit.defaultChromeURI"));
+
+  let val = Preferences.get("toolkit.defaultChromeURI");
+  Preferences.set("toolkit.defaultChromeURI", "test_lock_prefs");
+  do_check_eq(Preferences.get("toolkit.defaultChromeURI"), "test_lock_prefs");
+  Preferences.lock("toolkit.defaultChromeURI");
+  do_check_eq(Preferences.get("toolkit.defaultChromeURI"), val);
+  Preferences.unlock("toolkit.defaultChromeURI");
+  do_check_eq(Preferences.get("toolkit.defaultChromeURI"), "test_lock_prefs");
+
+  // Clean up.
+  Preferences.reset("toolkit.defaultChromeURI");
+}
+
+function test_site_prefs() {
+  let prefs = Preferences.site("www.example.com");
+
+  prefs.set("test_site_prefs.integer", 1);
+  do_check_eq(prefs.get("test_site_prefs.integer"), 1);
+  do_check_true(prefs.has("test_site_prefs.integer"));
+  do_check_false(Preferences.has("test_site_prefs.integer"));
+  prefs.reset("test_site_prefs.integer");
+  do_check_false(prefs.has("test_site_prefs.integer"));
+
+  prefs.set("test_site_prefs.string", "foo");
+  do_check_eq(prefs.get("test_site_prefs.string"), "foo");
+  do_check_true(prefs.has("test_site_prefs.string"));
+  do_check_false(Preferences.has("test_site_prefs.string"));
+  prefs.reset("test_site_prefs.string");
+  do_check_false(prefs.has("test_site_prefs.string"));
+
+  prefs.set("test_site_prefs.boolean", true);
+  do_check_eq(prefs.get("test_site_prefs.boolean"), true);
+  do_check_true(prefs.has("test_site_prefs.boolean"));
+  do_check_false(Preferences.has("test_site_prefs.boolean"));
+  prefs.reset("test_site_prefs.boolean");
+  do_check_false(prefs.has("test_site_prefs.boolean"));
+}
+
+
+function run_test() {
+  test_set_get_pref();
+  test_set_get_branch_pref();
+  test_set_get_multiple_prefs();
+  test_get_multiple_prefs_with_default_value();
+  test_set_get_unicode_pref();
+  test_set_null_pref();
+  test_set_undefined_pref();
+  test_set_unsupported_pref();
+  test_get_string_pref();
+  test_set_get_number_pref();
+  test_reset_pref();
+  test_reset_pref_branch();
+  test_reset_nonexistent_pref();
+  test_reset_nonexistent_pref_branch();
+  test_observe_prefs_function();
+  test_observe_prefs_object();
+  test_observe_prefs_nsIObserver();
+  //test_observe_exact_pref();
+  test_observe_value_of_set_pref();
+  test_observe_value_of_reset_pref();
+  test_has_pref();
+  test_isSet_pref();
+  //test_lock_prefs();
+  test_site_prefs();
+}