Read this blog post first: Do You Test Ruby Code for Thread Safety?

When you need to test your code for thread safety, what do you do? That's right, you just don't test it. That's wrong! This simple gem helps you test your code with just two additional lines of code.

First, install it:

$ gem install threads

Then, use it like this, to test your code from multiple concurrently running threads:

require 'threads'
Threads.new(5).assert do |i|
  puts "Hello from the thread no.#{i}"
end

You can put whatever you want into the block. The code will be executed from five threads, concurrently. You can also make sure the code block runs only a specific number of times specifying the argument in the assert method (it can't be smaller than the amount of threads):

Threads.new(5).assert(20) do |i, r|
  puts "Hello from the thread no.#{i}, repetition no.#{r}"
end

You can also provide a logger, which will print exception backtraces. It has to implement either method error(msg) or puts(msg):

Threads.new(5, log: STDOUT).assert do
  this_code_fails_for_sure
end

That's it.

Read these guidelines. Make sure you build is green before you contribute your pull request. You will need to have Ruby 2.3+ and Bundler installed. Then:

$ bundle update
$ bundle exec rake

If it's clean and you don't see any error messages, submit your pull request.