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TestR - Continuous testing tool for Ruby

TestR is a continuous testing tool for Ruby that automatically detects and tests changes in your Ruby application or test suite in an efficient manner:

  1. Absorbs test execution overhead into the master Ruby process.

  2. Forks to run your test files in parallel and without overhead.

  3. Avoids running unchanged tests inside changed test files.


  • Executes test files in parallel, making full use of multi-core CPUs.

  • Tests changes in your Ruby application: avoids running (1) unchanged test files and (2) unchanged tests inside changed test files.

  • Supports MiniTest, Test::Unit, RSpec, and any testing framework that (1) reflects failures in the process' exit status and (2) is loaded by your application's test/test_helper.rb or spec/spec_helper.rb file.

  • Logs the output from your tests into separate files: one log per test. The path of a log file is simply the path of its test file plus ".log".

  • Configurable through a Ruby script in your current working directory.

  • Implemented in less than 380 lines (SLOC) of pure Ruby code! :-)


Following UNIX philosophy, TestR is made of simple text-based programs:

  • testr is an interactive command-line user interface (CLI) for driver
  • testr-herald monitors current directory tree and reports changed files
  • testr-driver tells master to run tests and keeps track of test results
  • testr-master absorbs test execution overhead and forks to run your tests

You can build your own custom TestR user interface by wrapping testr-driver!

Usage and theory of operation

Run testr to launch the command-line user interface for testr-driver. It will present a menu of commands and then wait for you to input a command while the driver waits for testr-herald to tell it about changes in your tests.

When the driver hears about changes in your test files, it tells the master to fork a worker process to run the tests affected by those changes. This is all performed automatically. But what if you want to manually run a test file?

You can re-run any test file by simply saving it! When you do, TestR tries to figure out which tests inside your newly saved test file have changed (using diff and regexps) and then attempts to run just those. To make it run all tests in your saved file, simply save the file again without changing it.


  • Ruby 1.8.7 or 1.9.2 or newer.

  • Operating system that supports POSIX signals and the fork() system call.

    To check if your system qualifies, launch irb and enter the following:

    Process.respond_to? :fork  # must be true
    Signal.list.key? 'TERM'    # must be true


As a Ruby gem:

gem install testr

As a Git clone:

git clone git://
cd testr
bundle install


If installed as a Ruby gem:


If installed as a Git clone:

bundle exec ruby -Ilib bin/testr

You can monitor your test processes in another terminal:

watch 'ps xuw | sed -n "1p; /test[r]/p" | fgrep -v sed'

You can forcefully terminate TestR from another terminal:

pkill -f testr


TestR looks for a configuration file named .testr.rb in its current working directory. The configuration file is a normal Ruby script. Inside it, you can query and modify the TestR::Config object (OpenStruct) according to the configuration options listed below.

Configuration options


Maximum number of worker processes at any given time. The default value is the number of processors detected on your system, or 1 if detection fails.


Array of paths that are prepended to Ruby's $LOAD_PATH before the test execution overhead is loaded into testr-master.


Array of file globbing patterns that describe a set of Ruby scripts that are loaded into testr-master as test execution overhead.


Array of regular expressions that describe a set of file paths that cause the test execution overhead to be reabsorbed in testr-master when they change.


Array of file globbing patterns that describe the set of all test files in your Ruby application.


Hash that maps (1) a regular expression describing a set of file paths to (2) a lambda function yielding a file globbing pattern describing a set of test files that need to be run. In other words, whenever the source files (the hash key; left-hand side of the mapping) change, their associated test files (the hash value; right-hand side of the mapping) are run.

For example, if test files had the same names as their source files followed by an underscore and the file name in reverse like this:

  • lib/hello.rb => test/hello_olleh.rb
  • app/world.rb => spec/world_ldrow.rb

Then you would add the following to your configuration file:

TestR::Config.test_file_globbers[%r<^(lib|app)/.+\.rb$>] = lambda do |path|
  name = File.basename(path, '.rb')

In addition, these lambda functions can return nil if they do not wish for a particular source file to be tested. For example, to ignore tests for all source files except those within a models/ directory, you would write:

TestR::Config.test_file_globbers[%r<^(lib|app)/.+\.rb$>] = lambda do |path|
  if path.include? '/models/'


Lambda function that is given a line of source code to determine whether it can be considered as a test definition. In which case, the function must extract and return the name of the test being defined.


Array of lambda functions that are executed inside testr-master before a worker process is forked to run a test file. These functions are given:

  1. The sequence number of the worker process that will be forked shortly.

  2. The path of the log file containing the live output of the worker process.

  3. The path of the test file that will be run by the worker process.

  4. An array of names of tests inside the test file that will be run. If this array is empty, then all tests in the test file will be run.

For example, to see some real values:

TestR::Config.before_fork_hooks << lambda {
  |worker_number, log_file, test_file, test_names|

  p :before_fork_hooks => {
    :worker_number => worker_number,
    :log_file      => log_file,
    :test_file     => test_file,
    :test_names    => test_names,


Array of lambda functions that are executed inside a worker process forked by testr-master. These functions are given:

  1. The sequence number of the worker process.

  2. The path of the log file containing the live output of the worker process.

  3. The path of the test file that will be run by the worker process.

  4. An array of names of tests inside the test file that will be run. If this array is empty, then all tests in the test file will be run.

For example, to see some real values, including the worker process' PID:

TestR::Config.after_fork_hooks << lambda {
  |worker_number, log_file, test_file, test_names|

  p :after_fork_hooks => {
    :worker_pid    => $$,
    :worker_number => worker_number,
    :log_file      => log_file,
    :test_file     => test_file,
    :test_names    => test_names,

The first function in this array instructs Test::Unit and RSpec to only run those tests that correspond to the given test_names values. This accelerates your test-driven development cycle and improves productivity!

Configuration helpers

The following libraries assist you with configuring TestR. To use them, simply add the require() lines shown below to your configuration file.

require 'testr/config/rails'

Support for the Ruby on Rails web framework.

require 'testr/config/parallel_tests'

Support for the parallel_tests library.

Usage tips

factory_girl factories

Don't load your factories in master process (as part of your test execution overhead) because that would necessitate the reloading of said overhead whenever you change an existing factory definition or create a new one.

Instead, use at_exit() to wait until (1) after the master process has forked a worker process and (2) just before that worker process runs its test suite (whose execution is started by your test framework's own at_exit() handler):

require 'factory_girl'
at_exit { FactoryGirl.find_definitions unless $! }

This way, worker processes will pick up changes in your factories "for free" whenever they (re)run your test files. Also, don't load your factories or do anything else in your at_exit() handler if Ruby is exiting because of a raised exception (denoted by the $! global variable in the snippet above).

Known issues

Ruby on Rails

  • Ensure that your config/environments/test.rb file disables class caching as follows (NOTE: if you are using Rails 3, the testr/config/rails configuration helper can do this for you automatically):

    config.cache_classes = false

    Otherwise, TestR will appear to ignore source-code changes in your models, controllers, helpers, and other Ruby source files.

  • If SQLite3 raises one of the following errors, try using an in-memory adapter for SQLite3 or use different database software (such as MySQL) for your test environment.

    • SQLite3::BusyException: database is locked

    • cannot start a transaction within a transaction


Released under the ISC license. See the LICENSE file for details.

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