Remove unnecessary test seam

src/sidebar/util/postmessage-json-rpc.js

@@ -18,7 +18,6 @@ function createTimeout(delay, message) {
  * @param {any[]} params - Parameters of the JSON-RPC method
  * @param {number} [timeout] - Maximum time to wait in ms
  * @param {Window} [window_] - Test seam.
- * @param {string} [id] - Test seam.
  * @return {Promise<any>} - A Promise for the response to the call
  */
 export function call(
@@ -27,9 +26,11 @@ export function call(
   method,
   params = [],
   timeout = 2000,
-  window_ = window,
-  id = generateHexString(10)
+  /* istanbul ignore next */
+  window_ = window
 ) {
+  const id = generateHexString(10);
+
   // Send RPC request.
   const request = {
     jsonrpc: '2.0',

src/sidebar/util/test/postmessage-json-rpc-test.js

 import EventEmitter from 'tiny-emitter';
 
-import { call } from '../postmessage-json-rpc';
+import { call, $imports } from '../postmessage-json-rpc';
 
 class FakeWindow {
   constructor() {
@@ -19,20 +19,21 @@ describe('sidebar/util/postmessage-json-rpc', () => {
     let fakeWindow;
 
     function doCall(timeout = 1) {
-      return call(
-        frame,
-        origin,
-        'testMethod',
-        [1, 2, 3],
-        timeout,
-        fakeWindow,
-        messageId
-      );
+      return call(frame, origin, 'testMethod', [1, 2, 3], timeout, fakeWindow);
     }
 
     beforeEach(() => {
       frame = { postMessage: sinon.stub() };
       fakeWindow = new FakeWindow();
+      $imports.$mock({
+        '../../shared/random': {
+          generateHexString: sinon.stub().returns(messageId),
+        },
+      });
+    });
+
+    afterEach(() => {
+      $imports.$restore();
     });
 
     it('sends a message to the target frame', () => {