Add range tests for blob

[dlrobertson]

Add basic tests for a blob range request.

Related To: whatwg/fetch#1070

[dlrobertson]

Current status:

Test	Firefox	Safari	Chrome
Blob range request slices the blob	❌	✔️	✔️
Blob range request with multiple range values	❌	❌	✔️
Blob range request with short range end	❌	❌	❌
Blob range with no start or end	❌	❌	❌
Blob range with no end	❌	✔️	✔️
Blob range with no start	❌	✔️	✔️
Blob range request with multiple range headers	❌	❌	❌

[annevk]

Thanks for making these!

It would be nice to assert response.text() in all of these as well.

Have you considered creating an array-of-objects structure that you then for each so you can share all the assert and test boilerplate code? That might also make it easier to spot additional cases that need testing.

@jakearchibald might also want to take a look.

[annevk]

This is great! I suggest we add some more invalid cases here to cover more parts of the parser:

• bytes=x
• bytes 5-
• 5-
• bytes=5-x
• bytes=x-5

Other places we could add more coverage for is whitespace handling between the various tokens.

Let me know if you'd like some help. I can make some time to push a few tests.

[dlrobertson]

Other places we could add more coverage for is whitespace handling between the various tokens.

RFC 7233 doesn't seem to indicate a position on whitespace. Is this specified somewhere?

[annevk]

It does although in a convoluted way. See https://httpwg.org/specs/rfc7233.html#rfc.section.1.2 and https://httpwg.org/specs/rfc7233.html#collected.abnf for "normal" ABNF. It seems it allows whitespace in only a few places.

[annevk]

It seems I was wrong here, but I think we should still test cases like:

• bytes=5 - 10
• bytes= - \t5

They should probably fail given the RFC, but it seems like implementations are already not following the RFC for whitespace after bytes= so who knows.

Perhaps this is also a thing we can still tighten however.

[dlrobertson]

Based on some recent tests WebKit and Blink do seem to allow range specifications with whitespace like this...

[annevk]

This looks great.

Optional: add a test whereby the end is greater than the length (e.g., it's 100000) and test that it is clipped to the length.

Nit: (const) variables can just be called supportedBlobRange or some such, no need for all caps. Essentially think of const as variables that are not reassigned, not literally constants.