Implement blank file tests + fix shim

test/spec/shim/cast/Volume.spec.js

@@ -0,0 +1,17 @@
+"use strict";
+
+describe("chrome.cast.Volume", () => {
+    it("should have all properties", async () => {
+        const volume = new chrome.cast.Volume();
+
+        expect(volume.level).toBe(null);
+        expect(volume.muted).toBe(null);
+    });
+
+    it("should have expected assigned properties", async () => {
+        const volume = new chrome.cast.Volume(0.5, false);
+
+        expect(volume.level).toBe(0.5);
+        expect(volume.muted).toBe(false);
+    });
+});