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Watch any files in a directory, and take an action when they change (run tests, compile markdown, compile SCSS, etc).

Most of the code in here is written by Martin Aumont.


Please contact me if you would like commit access to this repository, or to help maintain this project.


observr is:

  • Simple to use
  • Highly flexible
  • Evented ( Listens for filesystem events with native c libs )
  • Portable ( Linux, *BSD, OSX, Solaris, Windows )
  • Fast ( Immediately reacts to file changes )

Most importantly it allows running tests in an environment that is agnostic to:

  • Web frameworks ( rails, merb, sinatra, camping, invisible, ... )
  • Test frameworks ( test/unit, minitest, rspec, test/spec, expectations, ... )
  • Ruby interpreters ( ruby1.8, ruby1.9, MRI, JRuby, Rubinius, ... )
  • Package frameworks ( rubygems, rip, ... )


On the command line,

$ observr path/to/script.file

will monitor files in the current directory tree, and react to events on those files in accordance with the script.


The script contains a set of simple rules that map observed files to an action. Its DSL is a single method: watch(pattern, &action)

watch( 'a regexp pattern matching paths to observe' )  {|match_data_object| command_to_run }

So for example,

watch( 'test/test_.*\.rb' )  {|md| system("ruby #{md[0]}") }

will match any test file and run it whenever it is saved.

A continuous testing script for a basic project could be

watch( 'test/test_.*\.rb' )  {|md| system("ruby #{md[0]}") }
watch( 'lib/(.*)\.rb' )      {|md| system("ruby test/test_#{md[1]}.rb") }

which, in addition to running any saved test file as above, will also run a lib file's associated test. This mimics the equivalent autotest behaviour.

It's easy to see why observr is so flexible, since the whole command is custom. The above actions could just as easily call "jruby", "ruby --rubygems", "ruby -Ilib", "specrb", "rbx", ... or any combination of these. For the sake of comparison, autotest runs with:

$ /usr/bin/ruby1.8 -I.:lib:test -rubygems -e "%w[test/unit test/test_helper.rb test/test_observr.rb].each { |f| require f }"

locking the environment into ruby1.8, rubygems and test/unit for all tests.

And remember the scripts are pure ruby, so feel free to add methods, Signal#trap calls, etc. Updates to script files are picked up on the fly (no need to restart observr) so experimenting is painless.

The wiki has more details and examples. You might also want to take a look at observr's own scripts, specs.observr, docs.observr and gem.observr, to get you started.


gem install observr

If you're on Linux/BSD and have the rev gem installed, Observr will detect it and use it automatically. This will make Observr evented.

gem install rev

You can get the same evented behaviour on OS X by installing ruby-fsevent.

gem install ruby-fsevent

See Also

  • redgreen: Standalone redgreen eye candy for test results, ala autotest.
  • phocus: Run focused tests when running the whole file/suite is unnecessary.
  • autoobservr: Provides some autotest-like behavior for observr
  • nestor: Continuous testing server for Rails



Run tests, compile markdown/SCSS/etc, when a file changes





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