Tests for syntax highlighting plugins
=====================================

Summary: Files in the "input" directory are edited by Vim with syntax
highlighting enabled.  Screendumps are generated and compared with the
expected screendumps in the "dumps" directory.  This will uncover any
character attributes that differ.

Without any further setup a screendump is made at the top of the file (using
_00.dump) and another one at the end of the file (using _99.dump).  The dumps
are normally 20 screen lines tall.

When the screendumps are OK an empty "done/{name}" file is created.  This
avoids running the test again until "make clean" is used.  Thus you can run
"make test", see one test fail, try to fix the problem, then run "make test"
again to only repeat the failing test.

When a screendump differs it is stored in the "failed" directory.  This allows
for comparing it with the expected screendump, using a command like:

	let fname = '{name}_99.dump'
	call term_dumpdiff('failed/' .. fname, 'dumps/' .. fname)


Creating a syntax plugin test
-----------------------------

Create a source file in the language you want to test in the "input"
directory.  Make sure to include some interesting constructs with complicated
highlighting.

Use the filetype name as the base and a file name extension matching the
filetype.  Let's use Java as an example.  The file would then be
"input/java.java".

If there is no further setup required, you can now run the tests:
	make test

The first time this will fail with an error for a missing screendump.  The
newly created screendumps will be "failed/java_00.dump",
"failed/java_01.dump", etc.  You can inspect each with:

	call term_dumpload('failed/java_00.dump')
	call term_dumpload('failed/java_01.dump')
	...
	call term_dumpload('failed/java_99.dump')

If they look OK, move them to the "dumps" directory:

	:!mv failed/java_00.dump dumps
	:!mv failed/java_01.dump dumps
	...
	:!mv failed/java_99.dump dumps

If you now run the test again, it will succeed.


Adjusting a syntax plugin test
------------------------------

If you make changes to the syntax plugin, you should add code to the input
file to see the effect of these changes.  So that the effect of the changes
are covered by the test.  You can follow these steps:

1. Edit the syntax plugin somewhere in your personal setup.  Use a file
   somewhere to try out the changes.
2. Go to the directory where you have the Vim code checked out and replace the
   syntax plugin.  Run the tests: "make test".  Usually the tests will still
   pass, but if you fixed syntax highlighting that was already visible in the
   input file, carefully check that the changes in the screendump are
   intentional:
	let fname = '{name}_99.dump'
	call term_dumpdiff('failed/' .. fname, 'dumps/' .. fname)
   Fix the syntax plugin until the result is good.
2. Edit the input file for your language to add the items you have improved.
   (TODO: how to add another screendump?).
   Run the tests and you should get failures.  Like with the previous step,
   carefully check that the new screendumps in the "failed" directory are
   good.  Update the syntax plugin and the input file until the highlighting
   is good and you can see the effect of the syntax plugin improvements.  Then
   move the screendumps from the "failed" to the "dumps" directory.  Now "make
   test" should succeed.
3. Prepare a pull request with the modified files:
	- syntax plugin:    syntax/{name}.vim
	- test input file:  syntax/testdir/input/{name}.{ext}
	- test dump files:  syntax/testdir/dumps/{name}_99.dump

As an extra check you can temporarily put back the old syntax plugin and
verify that the tests fail.  Then you know your changes are covered by the
test.



TODO: run test for one specific filetype

TODO: testing with various option values
TODO: test syncing by jumping around