test/shaping/README.md

Adding tests
============

You can test shaping of a unicode sequence against a font like this:
```sh
$ ./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:
```sh
$ ./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.:
```sh
$ ./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.