Test IE9 by mocking window globals

[etpinard]

which should help with @alexcjohnson 's #1297 and should be less annoying to setup / maintain than the appveyor CI.

[alexcjohnson]

Looks like a good test of the exact change I made here - thanks! 💃

That said, I'm not sure how realistic this approach really is, or could be made to be.

For one, a complete test would need to mock globals before importing Plotly, as some of the errors occur when the code is first loaded rather than when it runs (which, if we had done it in this case, would have necessitated loading a subset of the full bundle).

Also, simply setting a property of window to undefined is not enough, it would need to actually throw an error if you try to access it. Can you delete it instead? We could define a getter for it that throws an error, but then I'm not sure if typeof would could be made to yield undefined in case anyone looks for the property that way...

[etpinard]

For one, a complete test would need to mock globals before importing Plotly

Very good point here. Thanks very much. Here's what I came up with 4ce9df0

Note that each suite under test/jasmine/bundle_tests/ is run in a different browser window via the test_bundle.js task.

[alexcjohnson]

cool - can we also do something like

expect(function() { return ArrayBuffer; }).toThrow('ReferenceError: ArrayBuffer is not defined');

to make sure it's really inaccessible in the way it actually gets invoked in the code?

[etpinard]

done in 7cb691e

[alexcjohnson]

Nice, I thought it would be harder to get that to work! 💃