diff --git a/src/datascience-ui/interactive-common/redux/store.ts b/src/datascience-ui/interactive-common/redux/store.ts
index 7ee0e58627ee..ab045d4a4525 100644
--- a/src/datascience-ui/interactive-common/redux/store.ts
+++ b/src/datascience-ui/interactive-common/redux/store.ts
@@ -293,7 +293,7 @@ function getDebugState(vms: ICellViewModel[]): DebugState {
     return firstNonDesign ? firstNonDesign.runningByLine : DebugState.Design;
 }
 
-function createMiddleWare(testMode: boolean): Redux.Middleware<{}, IStore>[] {
+function createMiddleWare(testMode: boolean, postOffice: PostOffice): Redux.Middleware<{}, IStore>[] {
     // Create the middleware that modifies actions to queue new actions
     const queueableActions = createQueueableActionMiddleware();
 
@@ -304,8 +304,7 @@ function createMiddleWare(testMode: boolean): Redux.Middleware<{}, IStore>[] {
     // Create the test middle ware. It sends messages that are used for testing only
     // Or if testing in UI Test.
     // tslint:disable-next-line: no-any
-    const acquireVsCodeApi = (window as any).acquireVsCodeApi as Function;
-    const isUITest = acquireVsCodeApi && acquireVsCodeApi().handleMessage ? true : false;
+    const isUITest = postOffice.vscodeApi && (postOffice.vscodeApi as any).handleMessage ? true : false;
     const testMiddleware = testMode || isUITest ? createTestMiddleware() : undefined;
 
     // Create the logger if we're not in production mode or we're forcing logging
@@ -423,7 +422,7 @@ export function createStore<M>(
     });
 
     // Create our middleware
-    const middleware = createMiddleWare(testMode).concat([addMessageDirectionMiddleware]);
+    const middleware = createMiddleWare(testMode, postOffice).concat([addMessageDirectionMiddleware]);
 
     // Use this reducer and middle ware to create a store
     const store = Redux.createStore(rootReducer, Redux.applyMiddleware(...middleware));
diff --git a/src/datascience-ui/react-common/postOffice.ts b/src/datascience-ui/react-common/postOffice.ts
index 041432356cc1..55972153dac6 100644
--- a/src/datascience-ui/react-common/postOffice.ts
+++ b/src/datascience-ui/react-common/postOffice.ts
@@ -29,8 +29,8 @@ export declare function acquireVsCodeApi(): IVsCodeApi;
 export type PostOfficeMessage = { type: string; payload?: any };
 // tslint:disable-next-line: no-unnecessary-class
 export class PostOffice implements IDisposable {
+    public vscodeApi: IVsCodeApi | undefined;
     private registered: boolean = false;
-    private vscodeApi: IVsCodeApi | undefined;
     private handlers: IMessageHandler[] = [];
     private baseHandler = this.handleMessages.bind(this);
     private readonly subject = new Subject<PostOfficeMessage>();