Sort out sniffing tests

[annevk]

1. Find any existing tests.
2. Review them against the current standard.
3. Revise and write new tests.

[GPHemsley]

I don't remember what they do, but I have some tests here: http://whatwg.gphemsley.org/tests/mimesniff/

[annevk]

Once this is fixed, close https://github.com/w3c/web-platform-tests/issues/1851.

[dd8]

We've written some test cases - they're the source of issues from the last few days. Happy to contribute them, but not sure where they should go and they probably need some infrastructure (e.g. an HTTP server with a way of mis-configuring Content-Type for each test case)

[annevk]

@dd8 great; a subdirectory of https://github.com/w3c/web-platform-tests/tree/master/mimesniff would be the place I think. That also has such server infrastructure. Not sure how to run these from a browser though. Probably gonna have to be manual to some extent.

[dd8]

Hoping to do something that can be used for automated testing at implementation level - harder to automate using JS in-browser. At implementation level we'll do something this:

foreach ( test in JSON_testsuite ) {
assert( MimeSniffer.Sniff( test.inputMime, test.inputFile ) == test.outputMime )
}

driven by a JSON file like this:

  "All good text/html",
  {
    "inputMime": "text/htm",
    "inputFile": "test.html",
    "inputHeader": "",
    "outputMime": "text/html"
  },
  "Nosniff content-type text/html",
  {
    "inputMime": "",
    "inputFile": "test.html",
    "inputHeader": "X-Content-Type-Options: nosniff",
    "outputMime": "text/html",
  },

[annevk]

That looks pretty good. (I agree that we want a reusable setup like that. I was just wondering what kind of frontend we could use that would work across browsers. Perhaps some of it can be automated, for the resources that don't end up downloaded.)

[dd8]

For Mozilla you could use Document.contentType. For other browsers is there a DevTools API accessible within browser?

foreach ( test in JSON_testsuite ) {
 document.getElementById( "iframe_test" ).location.href = test.inputFile;
 // wait till loaded
 var actualMime = document.getElementById( "iframe_test" ).contentWindow.document.contentType;
 assert( actualMime == test.outputMime )
}

https://developer.mozilla.org/en-US/docs/Web/API/Document/contentType

[annevk]

Ah yes, contentType ought to be available in other browsers too (part of the DOM Standard) so maybe if they don't implement it yet, they will to benefit from these tests...

[domenic]

I think that'll only work for types that the browser puts into a Document, like images and videos. Ones that it tries to download (like PDFs in many browsers) or doesn't do anything with (like fonts?) probably won't work as well...

[annevk]

Yeah, we need a manual wrapper for the remainder I'm afraid (or possibly get a WebDriver hook).