Should have tests for error console

[wch]

This is a follow-up to #1060.

We should have the following two tests applications:

• One which tests that the error console correctly detects when an application has an input and output with the same name. There will be a visible error message as show below, and the error will be logged to the JS console.

• One which tests that when the same application is deployed to Connect, it will not show the error message. We want to make sure that the error console is not enabled when an app is deployed to Connect.

[karangattu]

Would you want to test the browser console as well for the first case or simply testing that the Shiny Client Errors popup is sufficient?

[wch]

I think testing for the popup is sufficient.