diff --git a/test/test-proxied-properties.js b/test/test-proxied-properties.js
index b7f62c2..f969d69 100644
--- a/test/test-proxied-properties.js
+++ b/test/test-proxied-properties.js
@@ -9,16 +9,48 @@ describe("browser-polyfill", () => {
     it("should proxy getters and setters", () => {
       const fakeChrome = {
         runtime: {myprop: "previous-value"},
-        nowrapns: {nowrapkey: "previous-value"},
+        nowrapns: {
+          nowrapkey: "previous-value",
+          nowrapkey2: "previous-value",
+        },
       };
       return setupTestDOMWindow(fakeChrome).then(window => {
+        // Check that the property values on the generated wrapper.
+        assert.equal(window.browser.runtime.myprop, "previous-value",
+                     "Got the expected result from setting a wrapped property name");
+        assert.equal(window.browser.nowrapns.nowrapkey, "previous-value",
+                     "Got the expected result from setting a wrapped property name");
+
+        // Update the properties on the generated wrapper.
         const setResult = window.browser.runtime.myprop = "new-value";
         const setResult2 = window.browser.nowrapns.nowrapkey = "new-value";
 
+        // Check the results of setting the new value of the wrapped properties.
         assert.equal(setResult, "new-value",
                      "Got the expected result from setting a wrapped property name");
         assert.equal(setResult2, "new-value",
                      "Got the expected result from setting a wrapped property name");
+
+        // Verify that the wrapped properties has been updated.
+        assert.equal(window.browser.runtime.myprop, "new-value",
+                     "Got the expected updated value from the browser property");
+        assert.equal(window.browser.nowrapns.nowrapkey, "new-value",
+                     "Got the expected updated value from the browser property");
+
+        // Verify that the target properties has been updated.
+        assert.equal(window.chrome.runtime.myprop, "new-value",
+                     "Got the expected updated value on the related chrome property");
+        assert.equal(window.chrome.nowrapns.nowrapkey, "new-value",
+                     "Got the expected updated value on the related chrome property");
+
+        // Set a property multiple times before read.
+        window.browser.nowrapns.nowrapkey2 = "new-value2";
+        window.browser.nowrapns.nowrapkey2 = "new-value3";
+
+        assert.equal(window.chrome.nowrapns.nowrapkey2, "new-value3",
+                     "Got the expected updated value on the related chrome property");
+        assert.equal(window.browser.nowrapns.nowrapkey2, "new-value3",
+                     "Got the expected updated value on the wrapped property");
       });
     });