Add failing test for load status code bug

[bedewilson]

Failing test for #1161. When the load() function returns a 4XX/5XX status code, but no error, the response resolves with status 200. The specified status code should be passed through instead.

As this relates to an instance where no error (apart from the status code) is provided, I have assumed that the error message should default to the standard http response string (e.g. specifying a 500 status code should result in an error.message of Internal Server Error.

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[benmccann]

Thanks. We can't really check this PR in with the tests failing. Do you plan to fix the underlying issue as well? If not, then this is still helpful, but I think the best course of action in that case would be to close this to help keep the review queue clean and then we can leave a comment on the issue referencing this PR or your branch so that whoever does fix it can use your test

[bedewilson]

Thanks - sorry did intend to but have been caught up. Happy to close for now and I will get to it over the next few days.