Thank you for your interest in contributing to fsnotify! We try to review and merge PRs in a reasonable timeframe, but please be aware that:

• To avoid “wasted” work, please discus changes on the issue tracker first. You can just send PRs, but they may end up being rejected for one reason or the other.

• fsnotify is a cross-platform library, and changes must work reasonably well on all supported platforms.

• Changes will need to be compatible; old code should still compile, and the runtime behaviour can't change in ways that are likely to lead to problems for users.

Testing

Just go test ./... runs all the tests; the CI runs this on all supported platforms. Testing different platforms locally can be done with something like goon or Vagrant, but this isn't super-easy to set up at the moment.

Use the -short flag to make the “stress test” run faster.

Writing new tests

Scripts in the testdata directory allow creating test cases in a “shell-like” syntax. The basic format is:

script

Output:
desired output

For example:

# Create a new empty file with some data.
watch /
echo data >/file

Output:
    create  /file
    write   /file

Just create a new file to add a new test; select which tests to run with -run TestScript/[path].

script

The script is a “shell-like” script:

cmd arg arg

Comments are supported with #:

# Comment
cmd arg arg  # Comment

All operations are done in a temp directory; a path like “/foo” is rewritten to “/tmp/TestFoo/foo”.

Arguments can be quoted with " or '; there are no escapes and they're functionally identical right now, but this may change in the future, so best to assume shell-like rules.

touch "/file with spaces"

End-of-line escapes with \ are not supported.

Supported commands

watch path [ops]    # Watch the path, reporting events for it. Nothing is
                    # watched by default. Optionally a list of ops can be
                    # given, as with AddWith(path, WithOps(...)).
unwatch path        # Stop watching the path.
watchlist n         # Assert watchlist length.

stop                # Stop running the script; for debugging.
debug [yes/no]      # Enable/disable FSNOTIFY_DEBUG (tests are run in
                      parallel by default, so -parallel=1 is probably a good
                      idea).

touch path
mkdir [-p] dir
ln -s target link   # Only ln -s supported.
mkfifo path
mknod dev path
mv src dst
rm [-r] path
chmod mode path     # Octal only
sleep time-in-ms

cat path            # Read path (does nothing with the data; just reads it).
echo str >>path     # Append "str" to "path".
echo str >path      # Truncate "path" and write "str".

require reason      # Skip the test if "reason" is true; "skip" and
skip reason         # "require" behave identical; it supports both for
                    # readability. Possible reasons are:
                    #
                    #   always    Always skip this test.
                    #   symlink   Symlinks are supported (requires admin
                    #             permissions on Windows).
                    #   mkfifo    Platform doesn't support FIFO named sockets.
                    #   mknod     Platform doesn't support device nodes.

output

After Output: the desired output is given; this is indented by convention, but that's not required.

The format of that is:

# Comment
event  path  # Comment

system:
    event  path
system2:
    event  path

Every event is one line, and any whitespace between the event and path are ignored. The path can optionally be surrounded in ". Anything after a “#” is ignored.

Platform-specific tests can be added after GOOS; for example:

watch /
touch /file

Output:
    # Tested if nothing else matches
    create    /file

    # Windows-specific test.
    windows:
        write  /file

You can specify multiple platforms with a comma (e.g. “windows, linux:”). “kqueue” is a shortcut for all kqueue systems (BSD, macOS).