Add push unregister test

packages/push/test/PushRegistrationTest.ts

@@ -53,4 +53,27 @@ describe("Registration tests", () => {
       }
     });
   });
+
+  describe("#unregister", async () => {
+    it("should fail to unregister in push server", async () => {
+      try {
+        await registration.unregister();
+        assert.fail();
+      } catch (_) {
+        return "ok";
+      }
+    });
+
+    it("should unregister in push server", async function() {
+      // in CI environment this test sometimes fails because of the default timeout 2s
+      // increase timeout to 10s
+      this.timeout(10000);
+      try {
+        global.window.localStorage = { getItem: () => "deviceToken" };
+        await registration.unregister();
+      } catch (error) {
+        assert.fail(error);
+      }
+    });
+  });
 });