Client conformance tests

[garretrieger]

Client conformance tests need to be designed and implemented. Possibly can use the existing in browser demo (https://fonts.gstatic.com/experimental/patch_subset/demo.html) as a starting point.

[skef]

Discussion in April 1 2025 meeting: may want to have tests output both as web pages but also in another form (eg. set of font files and expected outcomes) that non browser clients could use to test their implementations.

[svgeesus]

It seems we could get quite far with reftests, where the reference is a string of text and a link to a (non-IFT) font to render it correctly, and the test is the same text and a link to an initial subset that has one or more of:

• no glyphs for some characters
• no glyphs for shaped forms
• no ligature glyphs
• no support or some variation axes
• no support for the used portion of some variation axes

and thus, to pass, the correct patches have to be requested, downloaded and applied.

[svgeesus]

Testing was discussed during the 29 July 2025 call