Create tests for Disabled context menu items for unsaved files / #12806

[petetnt]

#12806 was merged without tests, but it might use some.

My post from #12806 outlines the tests as:

test/Menu-test.js sounds like a good place.

Any specific things you need help with the tests? The structure should could be something like:

it("it should disable context menu items when file doesn't exist ", function () {
 // runs create a new file
 // opens context menu
 // checks that all the items are disabled
});

it("it should enable context menu items when file does exist ", function () {
 // runs create a new file and saves it
 // opens context menu
 // checks that all the items are enabled
});
For example check `DocumentCommandHandlers` tests to see how the working set can be manipulated.