harfbuzz/test/shaping/README.md

Adding tests

You can test shaping of a unicode sequence against a font like this:

$ ./hb-unicode-encode 41 42 43 627 | ../../util/hb-shape font.ttf

assuming an in-tree build. The 41 42 43 627 here is a sequence of Unicode codepoints: U+0041,0042,0043,0627. When you are happy with the shape results, you can use the record-test.sh script to add this to the test suite. record-test.sh requires pyftsubset to be installed. You can get pyftsubset by installing FontTools from https://github.com/behdad/fonttools.

To use record-test.sh, just put it right before the hb-shape invocation:

$ ./hb-unicode-encode 41 42 43 627 | ./record-it.sh ../../util/hb-shape font.ttf

what this does is:

• Subset the font for the sequence of Unicode characters requested,
• Compare the hb-shape output of the original font versus the subset font for the input sequence,
• If the outputs differ, perhaps it is because the font does not have glyph names; it then compares the output of hb-view for both fonts.
• If the outputs differ, recording fails. Otherwise, it will move the subset font file into fonts/sha1sum and name it after its hash, and prints out the test case input, which you can then redirect to an existing or new test file in tests, eg.:

$ ./hb-unicode-encode 41 42 43 627 | ./record-it.sh ../../util/hb-shape font.ttf >> tests/test-name.test

If you created a new test file, add it to Makefile.am so it is run. Check that make test does indeed run it, and that the test passes. When everything looks good, git add the new font as well as new test file if you created any. You can see what new files are there by running git status tests fonts/sha1sum. And commit!

Note! Please only add tests using Open Source fonts, preferably under OFL or similar license.